D-Link DIR-655 :: Wi-Fi Signal Strong - Password Not Accepted

I bought this router (DIR-655) some time earlier this year, so it hasn't even been half a year that I've owned the thing.  I set it up in the small duplex I was sharing with my sister and it worked quite well.  Actually... for the first 45 minutes I was freaking out because I was getting practically no signal, then I realized I had forgotten to screw in the antennas... but that little anecdote aside, it worked fine.

I've since moved into a new place.  I got a new modem, still on Videotron, I just upped the speed from 7 MB/sec to 15 MB/sec.  Before setting up the router I inserted the CD that came with it and followed the instructions therein... things seemed fine, except that he automatically used the same network name that I used at my last place... almost like he was stuck on it.  I couldn't figure out how to create a fresh new network.  But  I shrugged it off and continued, entering my own password and everything else.

Now, at the end he gave me 4 pieces of information,

A router password. A network name (SSID), this is the one who's name was stuck to the old one. A network security type, I went for Most secure(WPA) And the network security key, this was a randomly generated alphanumeric code of some sort.

I copied this in two different ways and the installation wizard automatically saved me a copy onto the desktop, so I know for certain I got the passwords right.  I pulled out my iPad later, saw the network, a good strong signal, and tried to connect except it's not accepting my password.  The password I triple-saved and checked without a shadow of a doubt.  On a whim I tried to use the Security Key, and that seemed to connect for some reason, but it is considerably slower than it was at my last place.

The modem isn't to blame (it's running on double the speed now) and the signal strength is good.  It's just that something gone weird with the password, and it feels very slow.  Even if it wasn't slow, I would really like to know why none of my wifi devices are accepting the password I assigned.

And I used that http://192.168.0.1/ trick to look into the router settings from my computer.  I changed the network password into something new.  And still none of the devices will connect, they keep telling me it's the wrong password.  I am only able to connect through the Security Key and I don't like that!  I tried to contact D-Link's technical support the other day, but it drew on for so long my cellphone actually ran out of minutes. 

Short Version: None of my wifi devices are accepting the password I gave during the setup and I don't know why!

I'm running a 64-bit Windows 7 on 1-year old dual-core desktop computer.