Parents' extension approved: can they go to Canada?

[Hao]

Just got my parents extension approval for their visiting visa (application was submitted on 10/20/04). Now they want to visit my brother over in Vancouver BC, would there be any risk not being able to come back to US at the border? Their canadian visiting visa is still valid, and they visited my brother once in Aug 2004. I've heard that the risk is higher after filing for extension even it's approved. But I don't see why that would be that case. Would appreciate if anyone can share similar experience.

[immihelp]

I don't see any problem.