WiNCC ADODB problem

We have such a problem:

There is a VB script in the project for archive tag database query through ADO DB,
which is the same in WinCC_DemoProject_V62 (example for connectivity pack), where sql-query is used
"TAG:R,1,'0000-00-00 00:05:00.000','0000-00-00 00:00:00.000'"

In my script (on button click) there are 6 queries (for 6 archive tags) in comparison with the example above, where
the query is only one. Also the object "ADODB.Connection" is one.

Mostly the script is running well but sometimes the VB script engine hangs.
i.e. it can either work all the day long or freeze in an hour or right after the launch, no obvious regularity observed.
After freezing all the rest works well except for the VB scripts (VB thread doesn't as well as far as I understood).

If I deactivate the project then pdlrt.exe continues to hang in task manager processes.
And in two minutes WinCC advices to terminate it and reboot PC.
Without reboot the project won't launch.
Though if I close pdlrt.exe in task manager before WinCC notice then the project can be launched without reboot.

The script hangs in the following lines (I checked it with the help of HMIRuntime.Trace):
Set oCom1 = Nothing // "ADODB.Command"
Set oRs1 = Nothing // "ADODB.Recordset"
conn1.Close // "ADODB.Connection"
in "conn1.Close", to be exact.

In demo-projects (with the only archive tag request) several quick requests in a row contribute to the same
situation.

What can I do?

Connectivity pack is not installed. Do I really need it as the project can surely work without it...?
WinCC 6.2 SQL Server 2005 sp1+hf winXP sp2

By the way, is it possible to upgrade winCC sql server with service packs from the Microsoft web site?