This problem may be due to another cause but the most common occurance is when an image is opened from Bridge so I've posted it here. Here are the details.
I have had tons of problems with CS4 on my desktop PC but seem to have most of them resolved with a new video card, updated driver and help from an earlier thread. In fact, I thought all problems solved but this one has persisted. If it matters I'm running Windows XP service pack 3, 4gb of RAM of which 3.4 is available. It has an 2.67 GHz Intel Core2Duo cpu.
If I open CS4 and open an image, all paintbrush tools (paintbrush itself, clone tool, healing tools, etc) work fine. Sometimes I can work for hours with no problems. Other times these tools simply stop working. When this happens seems random. For example, the other day as long as I did not send anything to print, all worked fine but after printing a few images the tools stopped. Other times I've printed and the tools still worked. Sometimes if I open images direct in Photoshop using file -> open, all is well but as soon as I launch an image from Bridge, tools don't work. Other times launching from Bridge works fine, BUT more often than not, it seems to occur after launching from Bridge, hence the post here as I already noted. I've tried to trace down a common set of circumstances but it is too erratic.
What is interesting also is that the use of the tool shows up in the history panel as a step taken. There just is no visible effect on the image. This problem has been present since CS4 was originally installed along with several other problems. In the course of attempting to solve them all, I have deleted preferences and allowed them to rebuild, I have actually uninstalled and reinstalled Photoshop multiple times.
More confounding is that CS4 works fine on a clunky old laptop with less RAM and a much, much older video card. I also, as a test, ran the 30 day trial on the computer I'm using here. It too is older and less RAM and that worked fine too. So it seems to be saying there is something wrong with the computer used for photo editing or the video card. Don't think it's the card. I bought a new one. It didn't solve any problems so I bought another and it corrected many of the other issues I was having. Indeed after installing the latest drivers for this card, absolutely everything worked perfectly for almost two days but now this paintbrush tool issue is back.
So what the heck can be going on that is cumulative or is there a hardware component that is erratic or have I missed something in CS4? Man I love the power of the program and the improvements since CS3 but if I have to shut it down and restart it every single image, clearly that is not feasible.
Many thanks for any help.