My hypothesis is:
- you are running Ghostery as Chrome plugin or something similar so that e.g. your browser will block a couple of your scripts like the adstat thing and google analyticis
- your webserver has a problem sending the correct mime type for the javascript stuff. Check out this posting on the "resource interpreted as a ..." error message
It may be that only one frontend is not working correctly. This would explain why you get the errors not all the time.
In general your site is packed with scripts and images. The first page has > 250 requests & almost 4 Mb. That's very much and it takes time. Amazon's Frontpage has half the number of requests and something like 300kb.
You should check if you can reduce the number of requests - the yslow plugin may give you some good advise here. Can you reduce the image size and number of image? (css sprites?)
You should also check if you have to deliver all the images through your regular web browser or if you can use a lightweight alternative. Are you using NGINX? AFAIK it has good options for performance tunings.
Edit: As a starting point: http://gtmetrix.com/reports/www.ap.v11.pl/fBGKScZ6