Adam I think I now know what happened and it is partly my fault and partly Ebay. When I wrote first I was really upset so I was a bit sharp. I'm explaining it here for the benefit of any other users this may happen to.
It is a rather long winded explanation. You have been warned!
When I registered with Ebay my user id was a shortened version of my e-mail ad. Eg:
e-mail: somebody @ yahoo.com
id: somebody
these were the details I put into AS when I joined.
Subsequently I changed my registered e-mail address with Ebay. However, it must have taken them some time to update their records because they let me go on logging in with the old e-mail address for several weeks. And so I forgot about the change. Remember you can log into Ebay with either e-mail address or user id and I had told my computer to "remember" the little login script so I didn't have to bother filling out all the boxes every time. Well a few days ago (since my last successful snipe) Ebay began giving me error messages with this e-mail address so I began logging in with just my id of . I just put this down to one of Ebays not infrequent logging in glitches. But of course my "manner" of logging into Ebay no longer matched the details in AS so when the snipe came Ebay did not recognise it as coming from me!
Duh. Sorry. My fault. But if Ebay had updated their records earlier I would have sussed that something was amis before the all important auction and thought matters out as I have now had time to do.
Anyway I have now changed my AS preferences so that my details: e-mail address, id and password - all perfectly mirror what is in Ebay so, hopefully, next time I set a snipe all will be well.
I think the point i am trying to make is that users should make absolutely sure that if they change ANYTHING about their login script in Ebay then they do the same in AS to make them correspond. Otherwise they could FORGET about the changes and get caught out as I did.
Perhaps in the circumstances I don't deserve those 3 free snipes!