Altavista advertising causing drop from index?

Clients that advertise with Altavista dropped from index.

[Tenyque]

Two clients have been dropped completely from the Altavista index over the last month, both having substantially good standings. Most of our other clients enjoy good rankings with Altavista, with the only thing different about these clients being that these clients advertise through Altavista (Partner Listings, Banner/Skyscraper ads). Anyone else have an experience like this? Think I've found the cause of the drop?

[dwedeking]

I've had a few domains dropped in the last 6 weeks or so. Doing the same "style" of work on many domains that weren't dropped. None of them advertise on Alta Vista. So I don't think that advertising is it.

[Tenyque]

Thanks dwedeking, it is most likely a coincidence.
The idea of the only two clients being dropped completely from the index also happening to be the two that advertise is causing parts of my brain to fry.