I suspect it's 3.271. All 3.271 is 3.236 (Known Buggy version) with support for the CM19A added, so you get a buggy version that causes timers and macros to not work properly. Check the Forums for how to downgrade to 3.228, the last good version of AHP.
Does anyone here know why Dan always goes to the version first? That isn't always the correct answer. In fact, I haven't seen very many cases lately where it WAS the correct answer. Most of the problems I've seen lately have been signal propagation or noise issues, for which changing the software would not be the proper fix.
Try substituting an incandescent bulb in B3 fixture.
I will put in another vote for "it might be a noisy CFL bulb).
If you've read some of my other posts lately, you'd know that a bad CFL (my neighbor's) can put out enough noise to mess up an X10 setup across the street (mine).
As suggested by others, try a different brand, and see if that helps. You might also want to try manually (either from the software or from a PalmPad) triggering the lights in the sequence they would be done with the time (B2-On, B3-On, B2-Off, B3-Off), and see if that works. If not, then I would suspect the bulb in B3 first.
If you reverse the order (B3-On, B2-On, B3-Off, B2-Off), does it work? EVERY time?
If you see the opposite problem (B3 goes off, but not B2), then it might be both bulbs that are noisy.
I would try replacing both CFLs with incandescent bulbs, for testing. If everything works with the CFLs out of the picture, then it is likely that one or both of them is/are the source(s) of the problem.
Good luck.