If you use the default setup in lenny there should be no reason to upgrade. I have 2 machines here running lenny + ati cards, (4870 + 2600xt) and they both just work. 64 and a 32bit respectfully.
All I do to install the driver is ./ati-driver-installer-xxx.run with no arguments.
All I do to install the driver is ./ati-driver-installer-xxx.run with no arguments.
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