Could you tell us at what exact point do you get the 'invalid account' errors? When this occurs, are you actually running the Close Year function - or are you posting a batch with Closing journal entries?

- In the 3 Departments that are having the problem, if you go into the Edit Departments and pull up those Depts - do they have 300 listed in the 'Close dept to' account field?
- Is there anything in the dept field?
- In Edit Accounts - is there actually an Account 300 listed, and if so is it active (check the 'Account active?' checkbox in the General screen of the Edit Accounts for 300)?
- Is this account designated as an 'R' (Retained Earnings) account Type?

Finally,
- have you done any other processing in between the time you closed off the other 3 Depts and when you are trying to close these 3?
- Have you done a Data Integrity Check to see if the data shows any errors?
- Do you have a backup prior to running the Close Year function? (Just in case! )!