[LAD] Strange gettimeofday behaviour - out of order times.

I discovered gettimeofday occasionally gives me a time value which is less than a previous time value. The value is actually 'out of order' and really belongs ahead of a few others, according to examined printouts. So I tried clock_gettime(CLOCK_MONOTONIC, ..), same result. Then I tried clock_gettime(CLOCK_PROCESS_CPUTIME_ID, ..) and it appears to be OK so far, giving me what I want - truly linear time. Still checking some things, maybe there's a reason, the app's fault. From what I've read gettimeofday is thread safe, but the incorrect time values are being read by the same thread always. Any advice here, anyone seen this? Also, when using Jack, is it advisable to choose the same clock method as Jack is using (cycle, hpet, system)? Thanks. Tim.