I use VMware a lot, mostly using VMware Workstation 6.0.2 under Linux host. However, from to time, some or all of the modifier keys (Ctrl, Shift, and Alt) somehow ceased to function. Seemed that sometime VMware failed to correctly restore those keys function to X server.
Here's simple command, using xmodmap (installed as part of X base utilities) that will fix this issue. xmodmap is assumed to be located at /usr/bin