I noticed last week while helping out with the sponsor ads, that some of the ads didn't display on one computer while they do on the other. It took me a while to figure out, but I finally did..
In my case, it's Norton AntiSpam's ad blocking capabilities...
Turning ad blocking off, lets them show up...
Don't know if anyone else has been missing the sponsor's ads, but just in case, I thought I would share.