Mountains in Holland

Some time ago, I was very suprised to find mountains in Holland and yesterday, in the South of France, at FL 150 or so, I crashed into some peaks that seemed to reach far into the Stratosphere - something out of Lord of The Rings or Star Wars.
I, for one, wouldn't mind having some mountains in Holland, but that wouldn't be very realistic....It turned out this problem was caused by a "Light Weight Mesh" add-on I was using for Europe. At least, that's what I think, because I easily fixed the problem by removing this add-on. However, it left me with some intriguing questions:
1) What could cause this problem (other add-ons I've been adding lately, perhaps?)?
2) I've been using this add-on for almost two years now without any problems (I have FS 2002 PRO); how come it has started giving me trouble all of a sudden, and in different regions?
3) Is there any solution?
Thanks in advance for any answers.
PGW
I, for one, wouldn't mind having some mountains in Holland, but that wouldn't be very realistic....It turned out this problem was caused by a "Light Weight Mesh" add-on I was using for Europe. At least, that's what I think, because I easily fixed the problem by removing this add-on. However, it left me with some intriguing questions:
1) What could cause this problem (other add-ons I've been adding lately, perhaps?)?
2) I've been using this add-on for almost two years now without any problems (I have FS 2002 PRO); how come it has started giving me trouble all of a sudden, and in different regions?
3) Is there any solution?
Thanks in advance for any answers.
PGW