Comment 2 for bug 321694

Two possible reasons:
a) a huge timer hickup on the server
b) the server has LAG_CREDIT_SINGLE set to a high value and freezes for a bit

Variant a) would not explain why some people aren't affected, unless of course timer syncing behaves differently in different versions (it does, but the last change was before 0.2.8.2). Against b), a fix has been committed, the client now clamps the reports from the server as well.