Bad files, photos not loading right, crashing...really worried.

Question

Gosh lightroom and me are just not getting along lately. First my catalog destroys itself and then the following day lightroom on my husbands computer starts getting all wonky.
First, it wasn't displaying the edits in the little film strip thing at the bottom in develop like it usually does. I would have to click on the picture, it would show up raw and then load into all the settings we have done. Typically, once we edit a photo it just is that way from then on.
Then my husband gets back on his computer and works a little and all the sudden a bunch of files are having errors and none of the standard previews are loaded anymore. That is odd since we know FOR SURE we have loaded those and then did 1:1 previews on all the flagged photos we are working with.
Then after them being damaged it went back to most of them working. Freaking out...again...we just exported all the work we have done so far (about 95% of the wedding) so we wouldn't lose another wedding after the preview catalog crash. Now I am really uncertain as to what we should do...He shut down lightroom and we have not opened it back up again in fear we will screw something up. I thought I would do some research and write something here first since calling Adobe is useless after spending 2 hours on the phone only to not speak to anyone and be hung up on last time when my catalog crashed.
Lightroom is our life. We spend all day on it, do all our weddings in it...It is our workflow and our style. I can't do what I do in lightroom in photoshop since I have developed our style within lightroom. We have 8 weddings to edit and can't just stop working...
I guess i'm freaking out. Should we just export all our presets and delete lightroom and reinstall it? Do you think we have a bug? We work on macs so I would think a bug is much less likely than a windows computer? Could our version be bad? We are running on 2.4 I believe which is the most current? Should we go back to the previous version? We have not had ANY problems with lightroom until now and its like everything is going way crazy in the past 2 days so I guess i'm a little overwhelmed.
I'm honestly afraid to keep working in fear that all will be lost again. Someone told me about some XML thing that will for sure keep all our edits if something should go wrong. Is there a step by step of what that exactly means and how to make that happen?  I am much more of a creative artist than a programmer so I am a little slow on how a lot of things work on the back end.
Thanks so much for your help to anyone who replies. I just joined this forum a couple days ago and It is amazing how fast people do respond to things so I really appreciate it.

Answer 1

Holly,
a bunch of files are having errors
When you say "errors", what do you mean exactly? Do you get an error message, or is it just that the previews aren't showing up?
did 1:1 previews
By default, LR will delete 1:1 previews that are older than 30 days to free up disk space. Is that possibly what's going on?
Someone told me about some XML thing that will for sure keep all our edits if something should go wrong.
LR never alters the original image - all of its changes are stored separately as instructions (e.g. "Add 0.5 Exposure").
So when you see an image in LR, it gets the original image, applies every change you've ever made, and displays the result. The catalog (LR's database) keeps track of every single change you've ever made, and this is what you see in the History panel.
Optionally, you can instruct LR to save image data in what's called a "sidecar" file. This sidecar file is in Adobe's XMP format, which is based on XML. It will have the same name as your original RAW file but with a ".xmp" extension.
You can see this in action by opening the folder containing your original raw images - you will see DSC_1234.NEF (for Nikon) and it's "sidecar" file DSC_1234.XMP. You can actually open the DSC_1234.XMP file (but DON'T modify it) and see the XML that LR has created.
Another option is that if you are converting your RAW images to DNG, the same XMP data is written out, but it is actually stored inside the DNG file along side the RAW image instead of in a separate file.
The thing to watch out for is that a) writing the data to XMP is optional - you have to make sure you've enabled it (I don't remember if it's on by default), and b) the XMP file doesn't contain everything that's in the LR catalog, so you shouldn't view it as a substitute for backing up your catalog.
Also, while I know it's outside of the realm of your specific issue, it sounds like there are a few "workflow" tips that might help you out. If you already know this stuff, please feel free to disregard... much of this is personal preference and experience from having been burned in the past!:)
Set LR to test the integrity and backup your catalog every day. It only takes an extra minute but can be worth its weight in gold if your catalog ever gets corrupted. The cool thing about LR's backup is that it each backup is written to a new file - as opposed to just overwriting the same backup copy every time. In other words, if you backed up on Monday, Tuesday, and Wednesday, you would have 3 copies of the catalog: one from Mon, one from Tues, one from Wed. With normal backup procedures, you would just typically have the latest copy of the catalog - the problem being that if the catalog gets corrupted and you don't know about it, and back up that version, now you just have 2 copies of a corrupted catalog!
When you import, make sure to check the box that says "Backup To". This will immediately ensure that a) right of the bat you have 2 copies of each image, and b) ensure that no matter what you do in LR you will never lose your original image.
If you're really paranoid, after your import, shut down LR and back up your LR catalog, your RAW images, and your RAW images that were backed up as part of your import.
Make sure you have "write to XMP" turned on, or alternatively convert your RAW images to DNG. Either way will ensure XMP data is stored with your images. If you don't use DNG, make sure you back up the ".xmp" files as well as your your RAW (.nef, .cr2) files.
When you're done with your images, export every image to JPG. Back up the JPGs.
Periodically back up any LR presets and plugins
Peridocially burn your RAW images (either .CR2 + .XMP, or .DNG) and/or JPG to DVD, and store the DVD offsite (e.g. safe deposit box, friend's house). Alternatively, backup to an external hard drive and store off site.
Back up your entire system every night (or week or month - based on how much work you feel comfortable losing )
It might seem like a lot of extra steps, but much of it can be automated, and after a while it will just become part of your normal workflow. If you have to, keep a paper checklist next to your computer.
If you do this, you will have:
A daily backup of a known, good LR catalog.
A copy of every RAW image as it came off your memory card.
A copy of every RAW image and the latest edits.
A JPG version of every edited RAW image with edits "baked in"
A copy of your saved presets and plugins
Everything above backed up to a secondary location
Plus, a copy of RAW images and their latest edits and/or JPGs stored off site