Try deleting the file sitting in the workarea.
Eg: C:\users\[yourlogonname]\documents\Micro Focus\Net Express 5.1\Workarea\nxdebug~ds
I never remember which one of two solutions works.
The other is to rename the HKEY_CURRENT_USER\SOFTWARE\Micro Focus\NetExpress registry key, but you'd have to setup all your preferences again etc.
The onus is on you to take a backup :)
Neil