I call these bugs "bigressions". Add something, fix bug A and create bug B. Take it back out, and it fixes B, reintroducing bug A. It's a cycle in a graph. One of the reasons why version control rocks is that you should be able to identify these cycles, even when multiple developers ARE involved. Hopefully comments help you and other developers not to make such cycles last forever.

But these are good times to ask yourself about your unit test coverage, and also, about the possibility to refactor your APIs so that such problems become less likely in the future. 90% of patches seem to be of the "if SpecialCaseX then ExecuteHackY". And 90% of the cruft in all my apps seems to be these patches.

W