HELP! - Invoice is "stuck" - Can't do anything to it

[bigjoshc]

I am trying to apply payment to an invoice. But when I type in the customer's ID, nothing appears in it. So then I looked up the Invoice Number in the sales journal. When I bring up the transaction, no customer ID appears in the box. When I try to enter a Customer in, It says "Customer number , used in this journal, could not be found." I ran the integrity check and I get an I/O error on the journalheader. This invoice is 2 months old and I don't want to have to restore and re-key everything from that date. According to the G/L the invoice is posted. I can't void the transaction, or delete it (I get the same error message).What is going on? this is the only problem I've been having lateley.

Please help.

Thanks in advance,
Josh