I've posted this to the trouble ticket system, but I'm repeating it here to alert other Authorize.net users. Apparently in the last 48 hours Authorize.net has changed the way they handle decimals. Previously a transaction for $10 was handled as $10.00. Transactions now have 4 decimal places, so the $10.00 is now $10.000. As a result, charges are failing hash checks.

What does this mean for admins? It would appear that the transactions are being approved at Authorize.net's end - we're receiving the money; the problem is that the user gets a Hash Check Failed message and the forums don't update their membership level. Transactions are shown as "failure" in the transaction log, but are approved when you look at the report. End result: customer thinks the charge has not gone through, reattempts to charge, gets another error message, wash rinsh repeat until they quit. I've had to void more than a few charges as a result - if I don't