Heather I'm glad you reposted this!
The more I think about it- I think it might be a memory issue- the way you said it's fine for about 10 min.
Try this in photoshop to clear your clipboard and anything else in memory:
Edit>Purge>All
You can do this multiple times for a short term fix
If that works- it means that you are working with a small amount of RAM and it's filling up fast every time- low memory can do freaky things
Try this in Photoshop:
Edit>Preferences>Memory
Increase your maximum amount of memory allocated to photoshop- I set mine to 80%. (If you run another big photo editting program at the same time you won't be able to set it that high.) You have to restart PS for this to take effect.
Also, to free up some RAM you can do this:
Start>All Programs>Accessories>System Tools>Disk Cleanup (you can also run the defrag)
And at least once a week, if not more, I do this in windows:
Tools>Internet Options>General tab (temporary internet files)>Delete files
If you haven't done this for awhile it takes a looong time, but it's well worth it- this is one of the things that's done in the disk cleanup that I mentioned above
HTH- I know how frustrating computers can be!
