Dr. Jekyll and Mr. Foulmouthed Pissed-off Developer

Well, it looks like we may be losing the client I've been working with for two and a half years. Supposedly they're unhappy with the quality of our work, but strangely enough none of these problems started until we complained that they were three months late with our billings. They say that they're unhappy with my work because no one tests it, although I send everything to them for testing. This annoys me, and poses me with a conundrum...

The professional programmer in me says to keep working on everything promptly and doing my best until I receive word otherwise.

The spiteful nocker in me says that they can fuck themselves, that they're moved to the bottom of my priority list, and that I owe them nothing, since obviously our work was good enough to take without paying for it on time.

I try to listen to the former, but the latter keeps nagging at me with a string of curses...