A bit of a head-scratcher this one. Last weekend, my M52'd Touring refused to start. When turning the key, there was a 'click' from what I'm guessing was the starter solenoid but nothing else at all. I'd been commuting an hour a day for the previous few weeks without a sniff of trouble so this was out of character for the car. I thought it might be the battery, so I connected it up to my E46 330i to jump start it and it roared into life. Later on I checked all the fuses for a current drain but all was ok (thanks Si for your little fuse gadget

). I then connected it up to a battery conditioner and that showed that there were decent life in it so I left it for the rest of the day to give it a bit more juice just in case.
So last Monday morning I drove to work as normal but at home time it did the same thing - a click at the turn of the key but nothing else. I tried to jump it from a mate's car but it did nothing at all.
I've had a look at new starter motors from various places (anybody heard of RTX starter motors? Half the price of a Bosch item but I'm guessing there's a reason for that....

) but before I go down that route has anybody got and suggestions as to what might be wrong? I guess I'll have to have a crawl underneath to see there are any loose connectors etc.
I should say that it's got an M20 starter motor.
The only upside of having a dead E30 stranded at work is that I get to commute to work in my E3 3.0Si!
Anyway any thoughts/advice would be much appreciated.