It sounds like it's a memory issue, normally related to 'loose' search terms. If you are not searching through specific file types, e.g. DOC, XLS, TXT, FileLocator Pro will search through EVERYTHING it finds including DLLs, EXEs etc, which can quickly lead to very large result sets.
Please have a look at this post for information on reducing the memory burden of large searches:
How do I avoid "Out of memory" issues when searching very large repositories
You can see the current search state of the program by clicking on the 'View->Search Threads' menu option.
Also, if you have a chance click the Help->Generate Error Report if you think the software is stuck and it'll send more information about the state of the program to Support.
The "Filelocator Pro conversion Host" is a separate program that runs the conversion process for Office file types. Among other things it provides resilience against the conversion process cashing the main FileLocator Pro application.
If the conversion program does crash an error state will be logged against all files that were being converted at the time. FileLocator Pro should then detect the crash and re-launch the conversion program for files currently being queued for search.