I shoot on cf cards and bought cf 2 when i originally bought the camera. Thinking these could fail anytime i was out shopping and found a cf 1 card on the cheap having tried it a couple of times it doesnt seem to be compatible with my canon camera . Admittedly ive now stopped using it but id like to know what the difference is luckily i only seem to have list shots on a auto classic shoot zso wasnt connect with giving away
just puzzle as to why the difference only of the write speed
Some more modern memory cards utilise new protocols that older cameras simply do not understand and this may be the cause of the errors.
I have experienced this first hand with a 1DsII and a Sandisk Extreme Pro (SD) card I bought last year. The new card supports UHS-1 communication protocols yet the camera does not, ultimately what this meant was that the camera reverted to a basic compatibility mode when reading/writing and as such dropped the speed to 1x speeds (when it should have been something far higher like 66x). Cheaper (non UHS-1) SD cards work fine and are far quicker.
In the case of the D20 it may not support things like UDMA (and on Wikipedia they say it can only cope with 8GB formatting regardless of how much bigger the card is).