Ok, what ROM do you have?
Start/settings/system/system information
If it say a number less than A12 there then we know where to start.
You do have an X51v? not an X51 or X50?
The driver you linked to was an update for the Wifi, among other things, but it was for an X51 with QVGA, where you say you have an X51V which is VGA.
Try turning the WPA security off on your router and see if you get a connection then.
Make sure the router is set to Mixed Mode. B and G not just G.
I suspect it is the WPA, I don't think Axims like to connect to that.
Make sure you have entered the key correctly. I had that once when I had my keyboard set to another language, I kept trying to put in a y but was infact hitting a z.
It appeared to connect but wouldn't go anywhere, no wrong key warnings.
I assume you have looked at Ikehikers excellent
Wifi guide.