tedster - 3:31 am on Mar 24, 2012 (gmt 0)
@gyppo, Panda affects rankings. Your report is something others have noticed and it's not explained or understood very well so far - but it ain't Panda.
One possibility - at least in some cases - is a shift in Google Suggestions. If your search term disappeared (or even dropped lower) in Suggestions, fewer people would be even seeing the SERP where you rank well.
But again - Panda definitely affects rankings, not just traffic.