Out of Canada for more then 6 months, after app. for Citizenship, advice please

[canada_1]

First I want to say that this is the best forum I have every seen for Canadian Immigration :) And kudos to all members for helping people like me that don't know enough, I hope one day I'll be able to help someone as well.

Here is my problem i hope someone can shed some light on it.
Let me explain what is my case first.
 
1. I am permanent resident of Canada and I already filed for Citizenship approximately 1 year ago. I know that the waiting time for the test/oath has increased lately and this may take around 2 years until a date is available for the Citizenship test.
 
2. While I was living in Canada I had an ongoing family based petition for US ( my parents live in US ), granting me the right of a "Green Card". Just now ( February.2012, after 7-8 years ) i got a notice from the US embassy that Visa number is finally available so I can enter in US and get the green card. But I already live in Canada and I applied for Canadian Citizenship. Regardless i decided to go for the US green card at least to make my parents happy by visiting them.
 
3. While I was passing trough the security checks and the immigration office at the airport in Canada I was told by the US immigration officer that I can not hold 2 permanent resident cards ( Canadian and US ) which came as a surprise to me as this is the first time i hear about that. Regardless I told the immigration officer that I don't want to give up neither Resident card, because I already filed for Canadian Citizenship and without the Canadian Perm. Card I can't get the Canadian Citizenship which i defiantly want. After I showed a proof that I was accepted for the Canadian Citizenship test she let me go with both cards.
 
My question is:
Will there be any problem for me to stay in US until a date is available for the Canadian Citizenship and could that in any way be a problem at the time of the test ?
My brother is in Canada too and he is receiving my mail, so he can notify me immediately if I receive any mail regarding the Citizenship test.
What do I do?

Thank you for your help

[Leon]

There should be no problem.  There isn't actually any law as far as I know that states that you can not be a PR of two countries at the same time as long as you meet both requirements but the US seem to question your loyalties if you try this.

[canada_1]

Thank you so much about the quick answer, I highly appreciate your help Leon. I was surprised as well of what the immigration officer told me about the PR cards but what can i do I was like stunned when she told me you have to choose and give up one them... Anyway thanks again and God bless you for the support and the time you spend to help everyone in this forum.

If anyone else have similar experience or opinion please kindly share it. Thank you in advance.