Maybe this is bcos of the Adbrite2.0 . http://blog.adbrite.com/ It has the info about the Adbrite 2.0
For the last 3 or 4 days my adbrite didnt have many ads and just had an "advertise here" link on their banner. The rest was completely empty! No network ads displayed. So I just switched my site to bidvertiser. I heard bidvertiser got its act together recently so I will give them a try now. At least those ads are showing, another matter if anyone clicks them though.
i have noticed it being slow the past few days. the ads do show for me,but sometimes it wont show the network ads. the paid ads always show,their the ones that get the clicks anyway.
I'm a advertiser and I've noticed tweaks in their admin area. looks like they're still working on it. They're campaigns suck IMO - I don't see what the big deal is for upgrading to a new system.