I think I've tracked down the problem with my LJSync client. It's the opposite as I thought before. It looks to me like the server is returning to few entries, so my client gets confused and then tries to download the whole thing all over again. On my test of the "test" account it was expecting 818 but only got 812 so it started over, and thus got more then 818 and crashed.
So I've isolated the problem I'll try and work on a solution tonight. Thanks for all the testing.