Howe can it be that 5-6 campeigns leading to one landing page had millions impressions per day, and thousands of clicks/day went to absolutely zero impressions on all campeigns? Contacted Adwords, they say the LP quality is bad! I havn't changed the LP for months..and all of a sudden it went bad? Any ideas?
There's your answer - it's down to a low QS because: http://adwords.google.com/support/aw/bin/answer.py?hl=en&answer=66238