There are a couple things I see right off but I don't know if they would be the cause of data not being written. First, I would avoid using a character like "#" in your variable name. I would suggest using "visit" rather than "visit#". Also, you use "action = post" but it should be "method = post".
There is a nice demographics sample in the sharing area that shows the proper syntax for a variety of custom question types. See:
http://www.empirisoft.com/support/showthread.php?t=1091
If you make those changes and the data still are not showing up, make sure the variable name in the MediaLab questionnaire matches--e.g., in this case the ML variable should also be "visits".