FLV's and background converting

I don't know if this is a bug but version 2.4 so far has worked excellent except when uploading flv's with background converting on. The flv will upload ok and play alright but no thumbnail is produced. It's only with background selected cron and real time work ok. Anyone else have this problem?

just tested an FLV and it worked fine with background processing. there are 2 types of FLV file though....post the FLV file that had a problem and ill try uploading to my site