Has anyone ever encountered layer blend modes behaving strangely?

Question

I use photoshop quite a bit for retouching and photo compositing. Tonight I encountered a strange problem. I was trying to create a vintage look on a photo and had a number of adjustment layers including a curves, levels, color fill and there were also a few texture/noise layers all set to varying opacities. Near the top of all this I had a vignette layer that was black around the edges and white in the center set to blend mode of multiply. Well, when I was clicking on and off I realize that that vignette layer was definitely lightening the center part of the overall image quite a bit (the part that is white on the vignette layer), almost like a screen. So I flipped the vignette layer through different opacity modes and saw that there was no change in its behavior, every mode was screening the white, even darker color and multiply. I thought maybe it was interacting in a weird way with one of the other layers so I turned all the others off except the back ground-- still no change. Then I dropped the layer down one at time until it was below the background. When I started to move it up again, it was behaving normally for a moment until I moved it up a couple levels in the stacking order and then it went back to the screen behavior. Anyway I shuffled it around a bit but there was no consitency to when it would display the correct opacity and when it wouldn't, so it did not seem to be an interaction with any specific layer. I don't know, but I can't really think of any case where white set to multiply should produce a lighter result even if it were interacting with another opacity. In any case it does seem to me that there is something going on with the overall computation of opacities. I tried creating a new black and white layer and it was also doing the same thing, behaving strange and not displaying the correct opacity.
I'm tired, so I'm going to bed. I'm going to shut off the computer and hope this goes away when I reboot, but if it does not, does this sound familiar to anyone? I'm not a regular visitor to this forum, but I thought I'd put it out there in case anyone else has experienced anything like this. I've only got 5 gigs of ram on this computer and I've been working away for a while... maybe photoshop just couldn't keep up(?) I'm using Photoshop CS5, RGB Adobe 1998 colorspace.  I've never had anything like this happen in the last 11 years I've been using photoshop. Hmmm.... hope I don't have to reinstall or call support or worse. fingers crossed.

Answer 1

Nevermind. It is still having the problem. I have to think that this file is just corrupt somehow because I just opened another file and can't seem to cause the same problem. Basically, I can fill a layer with white, put it to a blend mode of multiply or darker color and it will block out everything of the image below, ie totally opaque. The opaqueness varies depending on the if there are other layers also on blend modes, but it does not seem to correspond to normal blend mode interaction. If I put it right on top of a regular layer with an image on it, it totally blocks it out on a blend mode of multiply... weird. I am going to scrap this file and see if the problem recurs in other files. My 2006 Mac Pro is getting some years on it and has been running pretty slow. I'm not a hardware expert but I've done everything I know how to do to maintain it. Was thinking of upping the ram to see if I can hold out a bit longer before I upgrade the computer. Wouldn't surprise me if this problem is related to the computer.