I have encounter the problem several times (not sure if it was that specific error#). I would recommend contacting the Ariba Help Desk with the problem number. They will walk you thru the process to see if you can replicate how the error message was generated. If I could replicate the problem, they were able to fix.
I am also the admin. I get this error at least once a week. Last week, it happened 3 or 4 times while I was doing invoice reconciliations. The help desk hasn't been able to tell me why this occurs. When it happens, I log back in and keep on going.