Application Error Msge after Upgrade (9.04.506c)

In the last month I've upgraded from 9.04.505a to 9.04.506c and now get random error messages that I can't seem to get rid of,...
Â
The biggest one (that causes my server to go down) is when we try and run a rather large report -- it hangs then gives the user two messages ---
 1st being ----
Error Detail
============
Object reference not set to an instance of an object.
Then
Error Detail
============
Tried to call a method in an invalid procedure. (7224)Â
Â
The error messages were record locking things until I tried going through the performance tuning with support from Epicor -- now I can't get my system settings back to they were before and keep my system from crashing.
Â
Â
Anyone run into these messages? Have any suggestions?
Â
It seems if the .xml file that gets created --- if it's larger than 65.5MB then it crashes.
Â
Thanks,
Laurie

[Non-text portions of this message have been removed]