unpredictable reboots using grub vga
i'm passing through grub the option "vga=0x346" to boot slackware 12.2 (kernel 18.104.22.168, default). randomly, after selecting slackware on grub, the computer just restarts. it rarely ever works; and when it does, i don't know why. i've been noticing that it _tends_ to work more often if i try it right after restarting windows, but it's not always the case. this used to work with my slackware 12.1 installation. i can always get in fine by taking out the vga option from grub.
other details: i am on a lenovo (ibm) thinkpad T500, with an ati radeon graphics card permanently set to discrete in the bios (as opposed to switchable between discrete and integrated), and the aspect ratio of my screen is 1.6 (1600x1050, although the option i passed was doing 1440x900). i thought it was a kernel config, so i've tried several different builds with different combinations of the vga/vesa/framebuffer options set. however, the results are consistently the same: rare successes and frequent reboots.