Weird Automation Error

I have a client-server application using DCOM:  The client side creates a remote object in the server side, and calls its properties and procedures when needed...  This has been working fine for years.
Just a day (user says that no -conscious- changes have been done in the system structure, neither software nor hardware) the applicaton begins to give an error at starting time:

"Automation Error 800706A7"

After analyzing the exact point in the program where the error raises, I see that it occurs when the client calls the first remote object function.  So, I deduce that DCOM works properly in the initial phases of connecting, activating the ActiveX server application, and creating the remote reference at the client side...

After a desperate search in the internet for the actual meaning of "800706A7" I got a mysterious sentence:

"The RPC protocol sequence is not supported"

Well... I do know that DCOM is just an implementation of RPC protocols.  So, I think that this mesage says that (in some -and mysterious- way) the call to the remote function is failing.

The fact of the system was previously working fine made me think of viruses, system file corruptions, automatic system updates and such, but the Windows System Restore did not fix the problem.

Environment description:
Application is written in VB6 SP6.
Network with 4 computers in the same workgroup, all with winXPpro. One of them works as server, and the other three are the clients. One of the clients has the problem, the other two ones continue working fine.

I would appreciate any comment.
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Martin LissOlder than dirtCommented:
i've never done anything with DCOM so take this with a grain of salt but from a search on the web it seems that you could be affected by the 'sasser worm'. Here's one of several articles that talk about it.

My Articles:
Using the VB6 DebuggerAutomatic Insertion of Procedure Names
A Textbox ActiveX Control That Limits Input to NumbersSpell Check a Textbox
Improved Formatting TagsConditional CompilationDynamically Resize Form Controls

Marty - MVP 2009, 2010, 2011

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asencorAuthor Commented:
I'm still waiting for the user to come back from his christmas/nwyear/winter hollydays... I will test the suggested solution as soon I can access to the system: I think  this week...

asencorAuthor Commented:
MartinLiss: Your grain of salt has hit the mark!!
I just downloaded and executed FxSasser.exe and it was like a miracle: All began to run fine.

In fact, I had thought of viruses, but I got misleaded by the fact that Windows System Restore didn't fix the problem...

Thank you very much!
Martin LissOlder than dirtCommented:
Glad I was able to help.
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