i'm glad to have found this site- i'm new to the bb world and love my 8220 flip. it does everything i need except acknowledge any memory card.
in options>memory i do have it set to read the card and i've tried 3 cards- 256mg (came with phone), 512mg & 4G. i think the 4G might be dead because my PC can't find it either but the 256 & 512 seem just fine but in options>memory it states that there is no card inserted.
Under Options (wrench icon) make sure Mass Storage Mode Support is ON.
At the bottom of the screen, there should be a section that shows your Application Memory Free Space, and under that, a section that shows Media Card Total Space and Free Space.
If that is not working, try pulling out the battary, with the phone turned on, for a minute or two, and then putting it back in. Battery pulls often sort out many different problems.