Corruption, typically, occurs on the File, not account, level … although it's certainly possible, if unlikely, that file corruption impacted only one of your accounts.
SO, start by taking a backup (just in case) and then just go thru the TOOLS, Account List menus and click ADD Account in the lower right corner of the dialog. Then move all of your existing transactions, in the old account, to the new account … disconnect the old account from download and connect the new account.
If that doesn't help, you've got the backup to restore from.
HOW DO I MOVE ALL OF THE EXISTING TRANSACTIONS IN THE OLD ACCOUNT TO THE NEW ACCOUNT?