How to avoid "Illegal to call out while in message filter"

I have a VB app calling methods in an object created in an .EXE automation server (written in C++ MFC).  Two different VB forms are accessing two different objects in the same .EXE server.  In general, things work fine, but I seem to get occasional collisions when both VB forms are accessing the server and one reports an automation error 0x8001005 ("Illegal to call out while inside message filter").  The one reporting the error is being wakened by a timer to make periodic calls (which work most of the time).  How is this caused and can it be avoided?
dho050198Asked:
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anthonycCommented:
sounds like a threading problem in the C++
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wokaCommented:
Check out articles Q176399 and Q138063 in the Microsoft knowledge base for some enlightenment about timers and the windows message queue and RPC in out of process servers.  You can use the timer, but you have to set some flags to avoid re-entrancy.
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Visual Basic Classic

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