There is a confirmed issue with conversion tracking on Google's Product Listing Ads (PLAs). A Google representative, AdWords' Bindu, said in a Google AdWords Help thread last night:
Known Issue: CPC PLA Ads Not Tracking Conversions Properly in the AdWords UI.
Our engineers are looking into this issue and hoping to have a fix very soon.
Please know that conversions don't affect how CPC PLAs serve. Any non-AWCT tracking that the advertisers may have used, such as Analytics, is not affected.
PLA's are product listing ads and if you are using these ads and paying for them on a CPC (cost per click) model, plus you are using Google's built in conversion tracking, the tracking is not working properly.
Bindu from Google said it has no impact on ad serving, it is only a tracking URL.
Forum discussion at Google AdWords Help.