I have some unit tests that are timing sensitive: an action is timed and an error is triggered if it takes too long. When run individually, these tests pass, but when running nosetest recursively on my modules, they often fail. I run concurrent tests, which likely is one reason why the timing is off. Is there any way to indicate that I want this test to be run with no interruptions?
I think your problem is dependent from how you implemented the timing. The solution I would personally adopt would be to set an environment variable that controls the behaviour of the tests. Candidates could be:

if WITH_TIMING == False [turn off timing altogether]
TIME_STRETCH_FACTOR = ... [apply a time-stretching multiplier in case of concurrent test are run, so that for example a time limit of 5 would become 7.5 if TIME_STRETCH_FACTOR would be 1.5]

If this is not an option, a possible ugly workaround would be to mock the time.time() function, making it return a constant value [this would only work if you use time.time() in your tests directly of course]...
HTH
Timing issues in Python nose test