I just tried it again and it isnt happening, but if its randomly doing that throughout the day it may be cause for your drop in sales.
http://img689.imageshack.us/img689/8408/81426076.jpg
http://img846.imageshack.us/img846/6210/52828067.jpg
http://img842.imageshack.us/img842/6282/11981201.jpg
http://img59.imageshack.us/img59/3449/30858638.jpg
you can see from the screenies that each tab is from a different url.
Some thumbs i clicked went to a site, most went to this error page, after like two refreshes the error page would go to the site it was supposed to go to but someone prob wont refresh a dead affil link multiple times imo.
Best of luck.