It is very likely that the user configuration file might be corrupted, you must delete this file and restart Multisim, this should reset your user interface configuration.
If you have version 9 or prior, it should be:
C:\Program Files\Electronics Workbench\EWB9\Multisim Users\<username>.ewcfg
If you have version 10 or higher, it should be:
C:\Documents and Settings\<username>\Application Data\National Instruments\Circuit Design Suite\10.0\config\standard_ms_uni.ewcfg
If you repair or reinstall the software, the installer does not modified your user config files and your user/corporate databases. That might explain why reinstalling did not worked.
Give this a try and let us know.
Nestor
