Just for info:
I have a UK 2009 E92 with the 6FL option.
Being a cheapskate I tried getting a cable off the internet and it didn't work - the IPhone 3GS never appeared on the iDrive. So I swallowed my pride and bought the official BMW lead (a bit of a rip-off IMHO). According to the parts man at the garage they've only ever had one type of cable and he told me up front it would NOT charge the 3GS. He was right. It plays fine but runs down if you do anything silly like listen to the IPhone and take calls on a drive longer than an hour or so...
So, I went back onto the internet and bought one of these:
http://cgi.ebay.com/ws/eBayISAPI.dll...m=270445089743
This now allows the IPhone to charge so I'm happy. Although heaven knows why some people get theirs charging without any help and some don't. Seems bizarre.