Comment 41 for bug 735126

And even if it does not block the installation for some reason, the installed system would not boot because of freezing on boot with KMS enabled. Though I only tried this with maverick->natty upgrade, but I guess it does not count at all, if it's an upgraded system, live system, etc, if it's kernel 2.6.38 it will freeze on radeon module, since afaik KMS is enabled by default in all cases and upstream only fixes this problem later, and it's not in natty's kernel yet. So I guess is affects every possible of usage/installation/upgrade method of natty on hardwares where it's issue - according to bug reports (including mine) it's at least Toshiba Satellite notebooks ....