J1 visa and US/Canadian residency

[ktgr8]

I am a Canadian living in the US with J-1 status. I have now been in the US for two calendar years, so I am considered a US resident alien for tax purposes for 2012. I am wondering if/how this affects my residency status in Canada. I do not have property in Canada, but I do have bank accounts, family, and the intent to return when my visa expires.

In 2010 and 2011, I was considered a US non-resident and Canadian resident for tax purposes and I have filed tax returns in both countries. What will be my status, and what returns will I file, in 2012?

Thanks for your help.