I placed a bid with myibay but when the time came for it to snipe, the auction ended and the bid was not placed. What could have happened

Just placing a bid is not enough to win an auction.
Your have to be the highest bidder and you must meet seller's and eBay's requirements as well.

You can always check your snipe status on your Snipe window in "My Status" field.
If you want me to look at it, please let me know your eBay user id and item number.

I placed a bid for 150.51 and the bid was not placed and was sold for 131.50, the bid that had been there all the time. There was no reason for me not to have won it unless the person that had the 131.50 had had a bid higher than mine. My ebay id is sunshine0055 and the item number is 260351837758

If you check "My Status" you will see the following:
"Refused login (password is too weak?)".

That usually happens when eBay consider your password is being too weak so I would suggest to update it.
Please check this forum thread for more information:
http://www.myibay.com/forums/viewtopic/1316/short-or-weak-password-will-prevent-you-from-bidding/

Please excuse me if this seems a dumb question ... but in the post above, are you talking about the Ebay password as being too weak?
If I use my Ebay password that I've used now for 4 years or more without any problem, then I shouldn't have a problem ... correct>

Thanks

(still finding my way around the software)

paraffinglow,
Not necessary.
eBay is constantly improving and strengthening their password system so whatever was good 4 years ago, may not be good today.

You may want to check if your password meets the following requirements:
http://www.myibay.com/forums/viewtopic/1316/short-or-weak-password-will-prevent-you-from-bidding/