pg crashing

Platform: Windows 2003 Server 32 bit
Windows SharedSection set to 1024,3072 based on recommendations from
http://www.postgresql.org/docs/faqs.FAQ_windows.html#4.4 and
http://support.microsoft.com/kb/184802
Version: "PostgreSQL 8.3.0, compiled by Visual C++ build 1400"
Autovacuum: on
Virus Scanning: disabled on PostgreSQL home directory
Problem: My database keeps on crashing every few days with this type of
error message:

2008-07-01 10:46:30 CDT LOG: all server processes terminated;
reinitializing
2008-07-01 10:46:31 CDT FATAL: pre-existing shared memory block is
still in use
2008-07-01 10:46:31 CDT HINT: Check if there are any old server
processes still running, and terminate them.

Is this problem fixed in 8.3.3 and/or fixed by moving to a Unix
environment like Solaris?

Jon