Cannot restart postgresql when increasing max_connections

Hi,

I have a server running 8.3.1 with 16Gb of memory and 8x2.5Ghz cores.  The max_connections was set to 100 (the default), but we were getting denied connections because it had exceeded the max.  We increased this to a modest 250, stopped the service, and then tried to start.  It wouldn't.  We stopped it several times, made sure all postgres-related processes were killed off but nothing would make it start.  Actually, it said it had started, but it hadn't.  When setting it back to 100 it was okay again.  We tried the same thing on another server, setting it to 1000, and that was fine.

Am I missing something?

Thom