Hmm.. I do know that, on a 190E, if you disconnect the switch for the rear left window, the front right window will stop working.
Not sure if that helps, but it does suggest if one switch/connection is bad it can stop 2 windows working..

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190E's:
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black 2nd owner
http://www.maylane.demon.co.uk/190esmall.jpghttp://www.maylane.demon.co.uk/190esmall2.jpg