See if http://support.microsoft.com/kb/980681 can help

>I have a program that uses the oMapiSession and oMapiMessage active X controls from msmapi32.ocx. Works fine under XP, Vista, etc. But when installing to SOME Windows 7 machines, it simply gets to the .SEND() command and does nothing. No error code, simply skips by it.
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>I've registered it by using a command line "run as administrator" and typed in: regsvr32.exe msmapi32.ocx. It succeeded.
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>It does work on some Windows 7 machines, just not on others. Any ideas or roads i can go down?