I spent most of yesterday and half of today trying to track down a bug in email sending from the billing system. We hadn't changed any code, but were suddenly seeing duplicate emails. Spent ages trying to find something wrong with the code, eventually just had to assume it was a system-level problem.

So, plaintive little email off to the sysadmin. He tries the test code and it works perfectly (no duplication). We try the tests again... no problem. Grr.

On the positive side, there's no TAUG meeting tonight, so I can work all night and try to catch up on the wasted time.

[Update: of course, the problem re-appeared this morning... sigh]