Don't have time to bisect today - 2.6.33-02468-g98b3188 booted yesterday with commit 9f7cdbc reverted.Never mind - some F12 update messed up mkinitramfs and/or mkinitrd.
I grabbed the panic with a cell camera - not much, so typing it here:
Kernel panic - not syncing: VFS: Unable to mount root fs ...
Pid: 1, comm: swapper Tainted: G W 2.6.33-04130 ... etc
Call Trace:
[<ffffffff815333d9>] panic+0x78/0x145
[<ffffffff81b2e241>] mount_block_root+0x1e7/0x29b
[<ffffffff81002930>] ? trace_kmalloc+0x1f0/0x8c0
[<ffffffff81b2e34b>] mount_root+0x56/0x5a
[<ffffffff81b2e4bf>] prepare_namespace+0x170/0x19d
[<ffffffff81b2d77c>] kernel_init+0x1b1/0x1c1
[<ffffffff8100bf24>] kernel_thread_helper+0x4/0x10
[<ffffffff81536b7d>] ? restore_args+0x0/0x30
[<ffffffff81b2d5cb>] ? kernel_init+0x0/0x1c1
[<ffffffff8100bf20>] ? kernel_thread_helper+0x0/0x10