Early build MKV's came with a AC compressor made by Zexel that was prone to failure of the antifriction coating on the swash plate, often causing compressor seizure. If you look at threads from 10 years ago you'll find a bunch of stories about cars stalling and needing a tow due to this issue. VW switched suppliers to Sanden in 07 or 08. The Sanden compressors are solid. You can tell which one you have by looking at the label on the compressor, and if you have a Zexel, I'd bite the bullet and replace it.