I've been trying for some time to install LMDE 64bit on my Toshiba C660 with ATI graphics card.
I seem to keep hitting a brick wall when attempting to run a live disc and end up at a blank screen. I get this result despite trying several installation discs. Mint 9 DVD seems to run with no problems but mint 10 has the same issues with blank screen.
I believe the problem is to do with the graphics card from googling and have tried various changes to the live cd/dvd boot options (set nomodeset & radeon.modeset=0) but with no success.
In the cmos menu (press F2 before boot), under the Advanced Tab there is a setting called USB Legacy Emulation. If this is set to 'Enabled' the white flashing cursor as described will flash for ever. If set to 'Disabled' Ubuntu fires up ok. 100% repeatable.