cciss driver regression, external array not mounted

Binary package hint: linux-source-2.6.20

We just upgraded to linux 2.6.20 and the external array (MSA30) on a HP DL585 (G1) was no longer mounted. Trying to mount it resulted in '/srv is already mounted or busy'. It's a staight ext3 FS, no LVM or anything is involved. I think the card in question is a Smart Array 6400. Downgrading back to the dapper kernel fixed it. There's a few caveats here though:

 (1) I was using the vanilla upstream kernel source (2.6.20.9), not ours - but we don't patch the CCISS driver
 (2) I was using a modularless (self-compiled) kernel with dapper userland
 (3) The external array is unhappy, it has a failed battery + (spare) drive - but it's still usable with dapper kernel

So I'm reporting it anyway especially since if this is reproducible with feisty it's an unfortunate regression. I'll try and stick some new drives into the machine and install feisty on it, to take (1) and (2) out of the mix.