I bought the same Patriot Mini SDHC 4GB card. It comes with a Mini SD to full SD adapter.

Popped the card into my N810. Seems to work at first. Followed KDE instructions to partition card and format in xterm. Then the N810 couldn't read the card anymore. File Manager tells me the card is corrupt and try repair or format. Repair doesn't fix it, and Format is greyed out. Popped it out and tried it in my PC. Couldn't read the card in WinXP - Windows Explorer hangs with hourglass until I pull the card out. Tried it in Ubuntu and it wouldn't add the drive (whereas my CF cards are detected and added automatically).

Exchange the card for another one. Tried it in my desktop first this time. Same behavior in my PC (hangs Windows Explorer with hourglass, not added in Ubuntu), so I thought I'd try another PC (XP) with another card reader. After XP detects the drive letters, none of the drive letters show the 4GB card. Autoplay pops up, goes away, pops up, goes away, etc... Tried the same card reader in a 3rd PC (XP) at home, and same deal as the 2nd PC.

Then I tried this 2nd MiniSD card in the N810. Finds it in File Manager, finds it in xterm.

Don't know what to make of it. Sure, I bought it to use as a mini SDHC card in my N810, but not being able to use it as a regular SD cards when needed doesn't make sense.