Photoshop Locks

After a year of use, Photoshop CS3 running on Windows Vista locks everytime I try to open a second file while I have one open already. I completely unistalled and re-installed the complete suite, but problem continues to exist. Anybody seen this?

Not something I've seen before, but resetting the preferences often fixes this type of odd problem in Photoshop. Re-installation does not reset your preferences.

To reset you preferences you need to do this;

Hold down Alt, Ctrl, and Shift keys (Mac: Command, Option, Shift) while starting Photoshop. A dialog box will appear asking if you wish to delete the preferences file.

Remember before you do this, to have saved any actions, styles, brushes etc. that you have created, as these are kept in the preferences file until you have physically saved them.