Have you been deleting files on your own? Usually what happens is that the uninstaller has a log of what was done to the system, and uses that log to uninstall the program. If that file was deleted, it can't run the uninstaller.
Sometimes some automatic file and registry cleanup programs delete these files thinking they are not needed, which is why I don't like using them.
Are you using the uninstall utility from within the program or from the Add/Remove control pannel utility? Try using the other method if you can. If the program was fairly recent, it would have an MSI database that Windows will use to run the uninstall rather than using the log file from Wise.