Can't get fglrx driver to work after recent xserver update (squeeze)

[Matteo Riva <muradin@gmail.com>]

After yesterdays upgrade which contained new xserver packages, I can't
run the fglrx non-free driver anymore. I installed the latest version
with the sgfxi[1] script but when xserver dies immediately with no
screens found and this error message

  dlopen: /usr/lib/xorg/modules/drivers/fglrx_drv.so: undefined symbol: Up

I can run the xserver deleting xorg.conf (which I guess defaults to
the foss driver) but the performance is poor.
Any help greatly appreciated.

  [1] http://smxi.org/