The Nokia Update wizard (Windows, currently version 1.2.2) will allow you to re-install the OS and should simply re-install the latest version of OS2008 if this is already on your device. http://europe.nokia.com/A4678158

Tip, you can also pre-download the OS prior to running the Nokia Update Wizard and this saves time in the future with updating to the latest and/or earlier versions of OS (You do not have to wait for wizard to download OS as part of update procedure) Follow the instructions here http://europe.nokia.com/A4680164

Make sure that once you have re-installed the latest OS on your device you switch it off, removing the battery to be sure it "Hard resets" the device.

Then before you try to install anything else, go to the Canola2 website and follow the install instructions for the N810
http://openbossa.indt.org.br/canola/install.html

Advise how you get on and will try and help you further if you are still having problems.