A week later: despite the router configured for WPA2/AES and the PC as WPA2/TKIP, no loss of connection since. Seems to be the solution. Sad.
Hi, I'm glad I found this post, I have a similar problem with my dell Inspiron 17R. So far rebooting the router works, and I have a stable connection for couple hours and then something happens and I cannot connect at all. All the other devices on the network work without problems, but my Inspiron not.
I will test tonight if changing the security setting resolves this issue.