I've been running it on an N800, but it's flashed with what I thought to be the same ITOS2008 that should be on the N810, so it should work.

Do you have much free RAM? I'm using my 2nd SD Card slot to expand my swap by an additional 128MB, though I'm pretty sure it's not neccesary for this game.

Maybe try downloading the swf file to your device with a "save link as" before you try to run it so your network connection won't act as a bottleneck.