Hello Dax,
Thank you for your question about this message. Yes, it's common for sellers to bulk list everything at prime time, around 7pm eBay time. We had to put in a "cap" that prevented, for example, 100 snipers to bid on 100 items in the same minute. That is 10K snipes, and so we wanted a safeguard to prevent a situation where we couldn't guarantee the accuracy.
Was this a one time thing, or are you seeing it daily?
Also - if I recall, you are using the API, correct?
bidslammer