Transaction ID Doesn't Auto-Increment

Hi,

Initially, upon upgrading to 3.0.11, none of my invoices, transactions, etc. are auto-incrementing upon creation. That is, I create an invoice and get a number - say INV-0019. However, 0019 is already taken, and when I try to save it I get an error saying it's already taken ... but it should've never allowed 0019 to be used in the first place! Invoice should have been created with 0020 as the number.

Now, a few weeks later, Invoices are magically working but Transactions still aren't(?!)

The administrative cost for this literally doubles my time - please fix immediately!
-Scott.

Update: bills and payments are also not working, in addition to transactions.

Where is the file/value containing the increment number and how do I reset it?

-S.