All SD form-factors are compatible, up and down, with an appropriate mechanical adapter. Just plastic and wires. So if it's not working, there's something wrong with the plastic and/or wires, most likely not making good contact at one end. No software solution is possible.

Very strange. I'm curious that Sandisk (which is the one reported in the bug tracker and that I have) would sell all these adaptors that don't do something as simple as make contact. Surely there must be something more to this than something that simple? Or can some readers somehow get away not needing all of the contacts whereas our N810s are more picky?

I don't have anything other than my N810 that takes a mini SD so I can't even test this...

One thing I did notice is that the micro SD doesn't appear to have a lock tab (i.e. thing you switch to make it read only) whereas the SD adaptor that I have has one of these. Does this simply switch one of the contacts on/off (presumably it actually does something , I've not tested it)?

AFAIK, the lock tab on the SD card has no electrical function and should be detected by the card reader and the OS then knows not to mount R/W?

I had the same problem with a SanDisk micro-to-mini adapter and a SanDisk micro SD card inside it. For some reason it is now working successfully. All I did was ejected the adapter and micro once more, then blew air into the adapter from different angles, then re-inserted micro and tried again to get the n810 to see the card. This activity felt more superstitious than pragmatic and could be merely coincidental. Needless to say, it is possible for a SanDisk brand adapter to work in an n810 mini slot. The micro was a SanDisk SDHC 8gb.

I had the same experience as the poster above. I went jogging with the n810 and it seems to have fixed it, but I wouldn't dare take out the SD card again. I use the cheap dealextreme.com micro to mini adapters. They look like sandisk knockoffs.