I also experienced this problem, the first time last week on the 19th. after reading a lot of discussions on the ebay boards, i came across an interesting point - that these captcha problems often occur on sundays, when the ebay bidding traffic is very high. my initial two times of this occurring happened last sunday. so today i was wary, and manually bid when i was able, with no problems whatsoever. but one of my snipes didn't go through and gave the ebay verification required message on auction sniper.
so, my theory is that *THIS IS A PARTICULAR PROBLEM ON SUNDAYS* and my experience is particularly in the *AFTERNOON*.
my snipes from the morning had no problem, but my snipe that was blocked was in the afternoon (CST).
i, too, rang ebay last week after this occurred, and had a customer service rep tell me that 'ebay does not recommend third-party sites' etc. they clearly know about the problem.
i believe that this is probably not an attack on sniping sites, but rather a glitch on their very shaky server, a problem with ebay's technology, given that it seems to occur especially when there is highest traffic volume.
any other folks have this problem on sundays particularly?