You said you use regtlib to register your tlb file and it didn't work. Are you administrator on that machine? If not there's a good chance that the registry has not been edited.
You could also try to move the tlb file in a subfolder of the LabVIEW folder, it sometimes help.
Another way to check if the tlb is registered or register manually a tlb is to use regedit.exe to manually edit the registry. The key is in HKEY_CLASSES_ROOT\TypeLib in the registry. After doing this and rebooting, the ActiveX class should be there. Be very careful when editing the registry and make sure to backup the registry log before editing anything.