Fan Problems

Hi everyone,
I have a 4x4x7 tent and a 440 cfm intake fan. This is my second grow with the fan and it did great last time. The problem I am having this time however is there just doesn't seem to be any draw coming from it. Previously, for example, I had been able to get the tent walls to suck in on medium speed (I have a regulator), this time it won't do it on high. I have the same filter ( 5 months old) and the only difference is I am using insulated ducting. Any ideas would be greatly appreciated.
Thanks,
Celticseas

Your intake hole isn't large enough.

Maybe what I mean is exhaust fan. I have it set up to suck the air out of the tent. I've thought that perhaps there were holes or something, but I don't see any and last time it would suck even with the flaps open. When I put my hand over the ducting I do feel air coming out, but it's just not that strong. Do you think it's the insulated ducting?