I had this same problem for a bit. What I had to do was add a '/s' to the regsvr32 command to suppress the dialogue/popup box on the remote server. If you don't suppress it, the remote server ends up waiting for user input it will never get, and subsequently 'hangs'.
My command in VisBuildPro ended up looking like: regsvr32.exe /s e:\path\to\my\dll
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