I've been having this problem ever since I installed Photoshop CS5 (12.0.4) on a Windows 7 64-bit machine. I've used the program on a Windows Vista 64-bit PC in the past with no problems.
Any color that has zero red information will turn black when in RGB mode and in either 8 or 16-bit mode. If I use the paintbrush, for example, a color with RGB 0/100/100 will be black. However, the color 1/100/100 will not. This problem also occurs with imported images. I've only tried JPEG and PNG so far. The problem does not save out though, as any image exported from Photoshop will appear fine. The issue seems to go away when in 32-bit mode, but it's a little RAM-intensive, and the file sizes are quite large.
I have reinstalled Photoshop, reset its preferences, and reinstalled my video card's drivers (I have a Radeon HD 7870). My PC has 8 GB of RAM and plenty of free hard drive space.
Below is a screencap of what's going on. I'm a bit lost here...any help would be greatly appreciated!
It's a well-known issue with current ATI drivers and Photoshop's GPU-accelerated color-management logic.
You can work around it a couple of different ways:
1. You can install ATI's latest Catalyst 13.2 beta driver, which does solve the problem, or you can uninstall and drop back to Catalyst 12.8.
2. You can switch to Basic GPU mode (and restart Photoshop). Basic mode moves the color-management logic into the CPU. This might be a workaround you'd prefer to take until AMD releases their next non-beta driver where the problem is solved.