Paul, regarding 6.5.3 I found this thread relating to downloading 6.5.3 but I don't know if the links are still valid:
http://forums.symantec.com/discussions/thread.jspa?threadID=69440&tstart=0
here are the fixes 6.5.3 contains:
LOR
A GoBack error was getting thrown
during install of LOR
-Fixed-
Drivers
BESR not able to load the SRD on
Stratus FTServers
-New drivers supplied from Stratus were added to BESR-
Disk Enumeration
BESR agent locks when GPT
partitions are encountered
-Fixed-
BESR ignores GPT partitions. Recovery points
may be stored to a GPT partition destination, however
BESR cannot create a Recovery Point of a GPT partition
Scheduling
"Error EBAB0013: A test that safeguards
the integrity of the program failed
unexpectedly. PRECONDITION failed,
TzSwitch::SetMonth:
\TimeZone.cpp(166): value >= 1&& value
< 12."
-Fixed-