Which security programs are you using? Some antispyware will see LW as a threat & delete the .exe (eg PestPatrol).
Have you upgraded/updated any security programs before this happened?
Limewire keeps disappearing! I have to then reinstall! help!!!

When I right click on the LW icon in the system tray, the options are Restore, About, Exit after Transfers & Exit.

Check your security programs and their settings