I’m sorry to hear that.
If you rearrange your workspace such that all the tools appear save the workspace as a custom workspace. When/if the tools disappear, select a different workspace and then select your custom workspace again. Do the tools re-appear?
All this shouldn’t be necessary, and personally I am not experiencing it under XP x86 or Vista x64, but the fact that you’re experiencing it means something on your system is coming into play.
Perhaps one or more of troubleshooting tips will help.
Cheers
Eddie