Doing catalog work on laptop when away from desktop computer

Question

I just recently moved from doing all my work on a single machine (laptop, MacBook Pro) connected to a 5 bay external hard drive to using 2 machines, a desktop (Mac Pro) hooked up to the 5 bay eternal HD and the laptop.
My set up - Desktop running Snow Leopard, Laptop Leopard. They are networked with an Airport Extreme. I log into the Desktop from the laptop rather than use File Sharing.
I'm still using Lightroom 2.7, single license, so I wouldn't have LR running on both machines at the same time. Catalog is stored on the Desktops internal HD - User/Pictures/Lightroom/Catalog. I use a single catalog, 30,000+ images. Catalog is approx 550MB.
I've got it pretty well figured out how to export a catalog from the laptop to the desktop after returning with images from a shoot, but, while I work a lot at my desk on the desktop, I want to be able to work on my catalog with my laptop. Hoping for some advise on how to do that. I'm looking to only do catalog type work on the laptop - evaluating, rating, deleting, keywording etc. I will not be doing any Developing or working on the actual image files, which are stored on the external 5 bay HD connected to the Desktop.
2 situations:
1. When I'm in another part of my space with my laptop and connected to my desktop (wireless), I go to the catalog located on the Desktop, I get a msg that Lightroom catalogs cannot be opened on network volumes. So how do I simply work on my LR catalog, using the laptop, when I'm networked to the Desktop?
2. When I'm away from my space, traveling etc, so not networked to the desktop. In this case I assume I would want to Export a copy of the catalog onto the laptop or a small portable HD and work on it while I'm away. But when I return, should I then Export the whole catalog back to the Desktop, or is there a Synchronize type function where LR updates the changes only? Is there a safe way to do this that minimizes the risk of introducing errors if the whole master catalog is moved back and forth? Should I break up my single large catalog in to smaller bite sized chunks that would be easier to move back and forth?
Thanks for any advise. If this is easier to accomplish on LR 3, that would be a good reason to upgrade. 

Answer 1

My master catalogs are heftier than I want to clone all over the place so I use the following method.
In LR, put the files you want to work on in a subfolder of your Primary catalog
Export Folder As Catalog with previews, but without including the DNG's
At your new location/machine work on that catalog.
Here's the part that's no fun, (obviously have a backup of your catalog before you do this)
In your primary catalog REMOVE that folder from your catalog. (this will remove all references within your catalog, but leave the RAW files alone where they were)
You then FILE-->IMPORT FROM ANOTHER CATALOG, and import your subfolder export back into your Primary catalog.
It'll bring all of your changes and previews back into your Primary catalog but with unlinked RAW files.
Click on the question mark in the corner of the thumbnail that's telling you it doesn't know where the source files are and LOCATE the original file again in your file structure, with the FIND NEARBY MISSING PHOTOS box checked.
Overly complicated for what it is, but it gets the job done.