I have had the same noise, I think.....not really a high pitched squeal, but a sort of mid to low range groaning noise, and always when just starting out in 1st gear on cold mornings. It didn't happen last year, but it was colder here this year. If the engine is at all warm...no noise. I took it in to the dealer, but they couldn't find anything, nor could they reproduce the noise.
It's going to get colder this week, so we'll see if the mystery groaning returns......The clutch doesn't appear to be slipping in any gear, and even putting it in reverse is not a problem. Maybe MCSs just don't like cold weather and are protesting....?

The engine in my S is completely stock, and the car hasn't been auto crossed for a year.
Even then, it was only a total of maybe 20 mins. and I didn't push it that hard, cuz I was just learning auto-x.

It's a mystery, wrapped in an enigma, bundled in a conundrum. I haven't a clue what's causing the noise.

 

Been having this noise go on for a few weeks now and I just took it in to the dealer this morning. Squeal, squack, honking noise when cold/humid/wet first gear only. SA at prestige said it was a normal thing for the cars. -- I was not real happy about that. The clutch does not feel bad or worn but if this gets worse I am not going to be real happy.

 

My MCS is 3 mos old but already has 8,000 miles on it. I was turning around yesterday on a slanted incline and it made the groaning noise while letting the clutch out in 1st. Then in stop and go traffic yesterday afternoon it did the same thing. &%*@! I have a trip to Tennessee planned for next month and will be introducing the MINI to my family <grin> I do not want them to hear this as they buy American cars mostly and I have been telling them what a great little car this is..

Making my appointment now.. wish me luck..

Craig