Welcome to mobileread ....
I wish I could help, but not owning a Kindle I can't. Mind my PB won't talk to my wireless router, either - but that's a WEP password issue !
That you managed to log on at a shop suggests it's a setting that needs to be tweeked.
Can you use USB cable for linkage ?
Have you had a look in the
Kindle Forum and even posted the question there ?