Hi,
I now have the same problem on my acer aspire 5720g. Trying the suggested steps does not work. It seems that the notebook is reading the USB thumb as it start blinking a little while, but the notebook never powers down (now waited about 10 hours as I went to sleep and left it powered on). Also tried it with CD. Same result.
If I power it off manually, then it is a brick like before.
Any hints? It's my parents notebook, so it is pretty urgent :-(
Thanks,
Markus