For instance, my ad will show for "blue widgets" but not for "red widgets" even though both of those are listed as keywords for the ad. It's even more frustrating for me; because, many of ads were at the premium spot. Now they're gone.
I did talk w/ a Google rep, and she said they are aware of the problem. However, there is no estimated time when the glitch will be fixed. Thankfully, she said "all engineers" have pulled from their projects to fix the system.
The only way I've been able to get my ads to show is to remove my negative keywords. Usually, I wouldn't even consider this, but I am missing out on some very time sensitive traffic.