How can i use the damn usb-key on Ubuntu??

Ubuntu has default to mount all usb drive automatically once you plug it it. There must be some problem with your installation or you might have accidently meddled with the seetings.

Your problem that your are not able to conduct net-banking is usually related to the Bankt itself, most websites are composed byusing the non-standard compliant MS FrontPage and their codes are usually only able to be interprated by Internet Explorer, other reasons are these website relies heavily on ActiveX (again a close source MS product).

Since you do not give specific error message about your failure to do internet banking, I am not able to help much here. Get back with more infor and I will try my best.

Reinstall ur Ubuntu driver of windows version or find the driver for linux from network like the Net-Banking's homepage.
Beside ,go to the bank where ur Ubuntu from and ask some guys for help.