I tooke my in-laws to Lawrence yesterday. It took more than 40 minutes for the agent to figure it out. In our case, my in-laws can apply. But unfortunately, we missed one basic document - the proof of address in ontario. Once we get that, we can go and apply. In summary, the document under this case needed are:
1) Proof to eligibility - the letter from the visa office asking you to pay the landing fee. -- we paid the fee in Feb. 2010 already.
2) proof of legally staying in canada - extenion of stay approval: my in-laws stay here from July 2009 and extend stay until Jan 2011
3) Proof of address -- phone bill, bank statement , utility bill etc. we will just open bank acct for them and wait for the statement.

Hope it help! Good luck!