These sync issues are annoying, we spent a lot of time diagnosing and fixing them. Unfortunately, some people occasionally still get stuck in a loop getting past long orphan chains.
Increasing the “temporary memory space” further used to audit the blockchain as it comes in, might start to cause other problems. I have made a note to increase the memory further for the next release, to reduce these edge cases.
Just in case there is something else causing an issue, which version of 0.9.6.2 are you using, the MAC? what is the CPU speed and memory?