For the last few days I've been messing about with an issue I first noticed on Friday (I upgraded to RC2 the day before as soon as it was released). The issue only occurred when in dual monitor mode, and then only in Develop, and further only on one of my catalogs (I have several mainly for Forum testing purposes).
The issue exhibited two characteristics:
1. Using Normal Loupe mode on Monitor two, making a selection in the Develop filmstrip on Monitor one would not always appear also on Monitor 2. I would get 'No Photo Selected' on #2, even though the Loupe View info for that image DID show on #2. However I could select another image and that would appear OK, and then go back to the first image and that would appear. Nothing overly problematic at this stage. However, I then found that any changes I made in Develop on #1 did not update to #2. Period. Just could not get the second monitor to reflect changes made on the first.
I wrestled with this for a while, and did things like export the catalog in total, and recreate the catalog by importing all images to a new clean catalog. Both the exported catalog and the newly created catalog did NOT exhibit the problem. Obviously I had optimised and integrity-checked the problem catalog, but no issues found.
2. So yesterday when I was doing some further checking, I inadvertently left Lightroom running on #1 (I had used both monitors, but I had reverted to just one) and I was using my web browser when I noticed it had got quite sluggish. So I called up Task Manager, and this is the display:
Wow, I thought....never seen RAM usage that high. You can see the effect when I shut down LR. Then restarted it, dual monitors, develop module, select an image, then do nothing but watch the RAM usage start to creep again. After 15-20 minutes of doing precisely nothing, this is the next Task Manager display:
Notice the CPU activity, with in theory nothing being done (browser shut down at this point). Note also that closing down the second window did not stop the RAM creep. Although I could stop both the RAM creep and the CPU activity simply by switching back into Library, this did not release the RAM until Lightroom was closed down.
Given the proximity of this problem first being noticed, and the RC2 upgrade, I went back and re-installed 4.0 and tested. No problem.
Then I upgraded to 4.1 RC1, and again no problem. My obvious conclusion at that point was that it's an obscure problem with dual window support in RC2 only.
Today I was going to write-up the problem, but decided to have one more go at nailing it a bit more. Given the fact that I now had 4 catalogs all at LR4 level, but only one exhibiting the symptoms, I looked more closely at the individual catalog settings. Interestingly, I found one obvious difference, and that was in the Standard Preview Size (File Handling tab of Catalog Settings). Normally, as both monitors run at 1920 resolution, I set the standard preview size to either 2048 or 1680....however the 'problem' catalog was set to 1024.
Can't be that simple, I thought....but sure enough as soon as I changed the setting to 1440 or higher the problem immediately went away. If I had both monitors active, make an extreme exposure change and not reflected on the second screen, see the RAM usage start climbing, then change the preview size and instantly the image on the second monitor updates and the RAM reverts to normal levels.
Apologies for the lengthy ramble, but thought anyone using dual monitors might be interested. Obviously I have no idea if it's just the 1024 setting, or if that is somehow related also to your screen resolution (i.e. if both screen and preview size are both at 1024, will the problem occur?).
By the way, I can also recreate the same problem on my single monitor laptop by opening the secondary window then dragging it to a larger (than 1024) size....if the window stays small, the problem does not occur.
PS: If anyone can confirm this, I'll post it in the official bug-reporting site.