Develop module sudden lag at start...

Question

I'd add this to the gigantic "LR is slow" topic, but it's a different oddity........
Windows 7, i920 at 3.8GHz, 12GB of memory, running LR 4.3 RC.  It was working better.  Yes, it's still not blinding fast or even as adequately fast as 3.6, but it was BETTER........
And it's been better for a couple weeks.  I've been able to start LR, look at images in the Library, go into Develop and have it display the preview fairly speedily, and so on...  Sliders and stuff weren't appallingly slow.
TWO DAYS AGO, for no reason that I can find, it suddenly reverted to behavior I used to see.  Still starts fine, still shows thumbnails fine, etc.  BUT, when I go into Develop, it puts up the preview, appears to finish and display the loupe text, THEN it starts the spinning wheel and just hangs there for 20 - 30 seconds saying "Loading".  It doesn't appear to be doing anything new, it's not generating (as far as I know) a 1:1 preview or opening another module, or doing ANYTHING IT DIDN'T DO LAST WEEK.  But, it definitely, consistently hangs for an extended period.  FWIW, when it does this, the background behind the loupe text goes from transparent to black, and it just sits there until it's done "Loading".
These are Nikon D300, dng files, so nothing large or interesting.  I haven't installed any new software or updates or anything else I know of in the last week.  I checked my cache partition and it's got 58 GB free.  I optimized my catalog yesterday.  I even deleted everything from the cache partition to see if that would matter.  It didn't.  I even rebooted the box just in case there was something else going on.  No difference.
OH, BTW, once it's done doing this, I can move from image to image in Develop and it NEVER DOES IT AGAIN...  It's only on initial entry.
I presume there's SOME setting, somewhere in LR that I changed or clobbered or did something to, but I have no idea what it is...  Hopefully the black background on the text will be a clue for someone.
Anybody have any ideas why I'd get this sudden change in behavior?

Answer 1

OK, whatever's going on, it's even more bizarre than I thought.......
I got rid of the agprefs this morning.  Started LR and it didn't make any difference.  BUT, I can repeat the problem easily, so I did some timing........
Start LR in library - 6 - 8 seconds - library's up, all folders filled in, everything's happy
Hit "Develop" with a standard D300 .dng file - 5 - 6 seconds for Develop to come up and the "Loading" to disappear
DON'T TOUCH ANYTHING............
20 - 22 seconds LATER the text background turns black as does the "not the current process version" exclamation point at the lower right.
Now everything just sits and spins for 18-20 seconds.  Once done, it's all happy and I can just process normally........
BTW:  I've REMOVED every lens profile I can find on the box EXCEPT those specifically for my cameras....  At present, I'm only loading (as far as I know) 41 total profiles as opposed to the hundreds that were originally there.......
To make it even MORE interesting - if DURING that 20 - 22 seconds after "Loading" ends and before it locks up I jump to a different image in Develop it NEVER LOCKS UP while in develop.  I can jump around normally and display any of the images.  BUT, if I do that, as soon as I hit the "Library" button, it locks up, the text background turns black as does the "not the current process version" exclamation point at the lower right and everything just sits and spins for 18-20 seconds.  Once done, it jumps back to the Library module.
Using the Task Manager, I can see that when I start LR in Library, memory jumps from a total of 2.88 GB to 3.1 GB, so it's not using a lot of memory.
When I hit Develop it jumps from there to 3.43 GB, so again not a lot of memory.
Watching the resource monitor, I can see a lot of disk activity at startup, but once the catalog is open it all appears to be in the temp folder...  As near as I can tell, the majority of the reading/writing appears to be in files that start with "etilqs" followed by a bunch of giberish and no file extension.
When I jump to Develop, I see a surge in disk activity, again mostly in temp, then it settles down and there's essentially nothing happening.
THEN, about 20 seconds later, when things hang, the resource monitor shows that the Lightroom image is NOT RESPONDING.  I don't see any disk activity in the resource monitor, but since it's "not responding" I'm not sure activity would be displayed.  BUT, I also don't get an activity light on the disk.  So, if there IS disk activity, it's so short the LED isn't lighting long enough for me to see...
I've emptied every "Temp" folder on the C partition just in case...  Once I shut down Lightroom, I have TWO files in the temp folder.  I'm not sure EITHER has anything to do with Lightroom, and even if they do, I'm not sure what they indicate.  One is "cr_sdk_71165937.tmp" which is "0" bytes.  The other is "FXSAPIDebugLogFile.txt", ALSO with a size of "0" bytes.
And AGAIN, I've had 4.3RC on for about 3 weeks and the system DID NOT DO THIS PRIOR TO LAST SUNDAY...  My workaround at present is to stay out of Develop until I'm ready to go in with a bunch of images to edit, so it's annoying but not a productivity killer.  But, it'd be really nice to find out what I did that's causing this behavior.