The problem is solved by registering the Worksoft.PerfItfc.dll (aka PerfItfc2).
For Windows 32-bit operating system:
%windir%\Microsoft.NET\Framework\v2.0.50727\regasm
"C:\Program Files\Worksoft\Certify\Client\Worksoft.PerfIftc.dll"
/codebase
For Windows 64-bit operating system:
Use a different path for the .Net framework. (You'll need to find out the .Net framework path on the machine):
<the .net framework path>\regasm "<worksoft install path>\Worksoft\Certify\Client\Worksoft.PerfIftc.dll"
/codebase
For Citrix Xenapp environment or Terminal server:
Please first put the Citrix server in install mode from the DOS prompt (Change User /install) before registering the DLL and then put it back into execute mode afterwards (Change User /execute).