Crashing since 8.4 upgrade

[pseconds]

I upgraded from 8.3 to 8.3 on Windows 2003 - now it appears the server is crashing every 24 hours, however it is happening at different times during the day. I have not found a pattern for it. I do not have very many domains on this server, low traffic.

Anyone else having the same problem? Server has been very stable for quite a long time. My event log is pretty vague...