We have had a few Customers call in recently, after seeing this error whilst modifying a SolidWorks installation to add in the Vault Admin Tool.
I have seen other posts on here that have resulted in a complete removal and reinstall of SolidWorks to fix, but this shouldn't be necessary.
Modify your SolidWorks Installation and remove SolidWorks Explorer, then modify the Installation again, adding in SolidWorks Explorer and the Vault Admin Tool and it should all go on fine.
Hope that helps somebody!
Customer Support Manager