Under Windows98 and WinME, many users are getting into a state where most commands report a program error and fail to function. This same problem can cause crashes in the magnetic lasso and magnetic pen tools.
A1: After they start, show the about box for any plug-in, then continue working.
A2: Select the Adobe PostScript printer driver as you default printer.
Details: many printer drivers on Win98 and WinME leave the CPU in a bad floating point state, and that bad state remains when Photoshop tries to use floating point code. Photoshop receives a floating point error from the CPU that it doesn't know how to deal with, so it reports a generic "program error". Showing the about box of a plug-in will reset the CPU to the correct floating point state. After that, everything should work -- until the next time you access anything about that printer....
Using the Adobe PostScript printer driver avoids the floating point state problem entirely.