Can you check which Arnova 8 G2 model you have (8G2, 8bG2 capacitive, 8bG2 DT) ? 

Which firmware have you flashed ?

If you are sure you have a 8G2, not a 8bG2, the problem could come if you have a tablet wirth 4 Gb storage.

8 G2 firmwares are compatible only with the 8 Gb storage models as the Blog article clearly states.

If you have a 8 Gb model, you need to reflash a firmware with Rockchip flashing tool:

http://www.arctablet.com/blog/featured/flashing-arnova-g2-rockchip-2918-rockchip-flashing-tool/

You can try Morkamod: http://www.arctablet.com/blog/forum/arnova-g2-general-discussions/morkamod-android-3-honeycomb-look-on-arnova-7g2-8g2-9g2-and-10g2-releases-topic/

or the stock firmware (see at the end of the Blog article: http://www.arctablet.com/blog/featured/arnova-8-g2-first-custom-firmware-android-market-root/ )

If you have a 4 Gb model, there is currently not firmware dump for that tablet. I hope that one will be dumped soon, I have made a request here: http://www.arctablet.com/blog/forum/arnova-8-g2/looking-for-arnova-8-g2-4-gb-model-firmware-dump/

As I said, you can't reset your device to the factory firmware as it has been erased when you flashed a new firmware.

You'll need to flash a firmware for the 4Gb model when someone makes a dump from this model, there is none at the moment.