Error 58186 "Full Text Search execution failed. External module has reported an error."
Generally this is because the Microsoft Index catalog has become corrupt. This can happen for various reasons, as Microsoft explains here http://support.microsoft.com/kb/209304 Bentley support can provide a tool to test a search of the catalog directly to verify if this is the case
"Catalog corruption is most commonly caused by the following:
Also from Microsoft (http://support.microsoft.com/kb/209304)
Stop Microsoft Indexing service
Delete catalog.wci (default directory C:\ProgramData\Bentley\index-storage)
Start Microsoft Indexing service
The calalog will be recreated using the data already extracted out of the ProjectWise files.