maybe $10 is so high they rejected it? similar to adding a zero on a stock purchase at etrade - they'll call you and tell you you overbid...
c1.xlarge on US-East charts: linux - http://cloudexchange.org/charts/us-east-1.linux.c1.xlarge.ht... windows - http://cloudexchange.org/charts/us-east-1.windows.c1.xlarge....
Try offering $1.30 if you need linux or $0.55 if you need Windows.
I just submitted several more otherwise identical bids at different prices to see what happens...