The problem here isnt the old card, its the shared memory design of that card.
All graphic cards with shared memory suck and gave problems. they are cheaper, but they are a mess. ATI ones never got any love, even from their engineering, so that shared memory graphic cards are just plain hacks to reduce cost.
ATI shared memory cards always gave several problems in all OS, had a bad performance and had unresolved bugs. No ones want to try to solve the problems of a obsolete and troublesome card. So instead of running buggy accelerated drivers (that can crash your machine), its better to use vesa, unaccelerated but stable drivers. the performance difference between the two isn't that great either.
If you want to use accelerated drivers on share memory graphic cards, try to fix it your self, or finding someone who might want to work on it.