[Sat May 24 02:02:51.025715 2014] [:error] [pid 14334] [client ***] ModSecurity: Access denied with code 400 (phase 1). Operator GT matched 512 at ARGS_GET:_uids
such params should be POSt and not GET
affects mailboxes with a lot of messages and seems to be a very new problem with RC 1.0.x
I think (not 100% sure) UID is passed with the URL to make messages cacheable.
Displaying messages -> Cache messages