Goods receipt Purchase Order error (MIGO_GR)

Hi

I'm trying to save this transaction but it is giving me an error message.

The message comes up as -

*" User ******** already processing Purchasing document **************"

This message has been there for 5 hours now

We have tried few things but this document is stuck somewhere and we don't have this document number is our system. Is there anything I can do to find out what happened?

Thanks and regards