I also had minor to major issues with my 2000 Volvo S40 1.9T. The list are as follows:

1) Fog lights kept on flickering. The cause was poor wiring. The fix was they had to rewire them so they will not clamp next to the body.
2) A/C unit was dripping water and misting. Cause not known but they decided to replace the condensors.
3) Car would not start. Cause was bad ignition unit. The fix was to replace the ignition unit.
4) Sunroof rattles. Cause was the the visor was loose. The fix was none. They could not reproduce it even though the head mechanic test drove the car with me and heard the same noise.
5)Rear breaks gone at 11,000 miles. The fix was had to replace them both. Front was already at 50% left.
6)When backing up a loud pitch squeel was heard. Cause was driver side brake pump was bad. Fix was replacing the bad brake pump.
7)Everytime I accelerate when the temperature was below 35 degree I could hear a grinding noise coming from the passenger side. Cause was the engine mount was faulty. Fix was replacing the engine mount.

I think the 2000 Volvo S40 was a bad year for the car since it was the first for US. Later model does not seem to have major issues like the ones I had. I only had 1 more year left on the warranty and decided not to chance it so I traded in the car for an Audi A4. Since Volvo has been discounting the S40 considerably the valuation of the S40 are extremely low. Only got $13,000.