terrible design by microsoft. i have 6 standard controllers and 4 of them have malfunctioning 3.5 ports right now. all are less than 12 months old and 3 of them are less than 6 months old. pathetic. moral of the story:
1) talk to microsoft, if your console is still under warranty i believe they will replace for free.
2)if not under warranty just buy a replacement or
3)try the above steps to fix it and if things go wrong and you bust it see step 2