may need to reload taskman.exe
both the commands should open taskman
sounds like you gotta bug
the easyest way I have fixed it is by reloading taskman from disc
find taskman.ex_ this is compressed file
go to MS on the net and get instructions on how to unpack and copy to system folder
must run under command line
you can also try this
Hive: HKEY_CURRENT_USER
Key: Software\Microsoft\Windows\CurrentVersion\Policies\System
Name: DisableTaskMgr
Type: REG_DWORD
Value: 1=Enablethis key, that is DISABLE TaskManager
Value: 0=Disablethis key, that is Don't Disable, Enable TaskManager