Here are the addresses of the various versions of 2.3.3:
Kindle2(US) :
http://www.amazon.com/update_kindle2.bin
Kindle2(Global) :
http://www.amazon.com/update_kindle2_gw.bin
KindleDX (US):
http://www.amazon.com/update_kindle_dx.bin
Kindle DX (Global):
http://www.amazon.com/update_kindle_dx_gw.bin
Try downloading the bin for your type of Kindle and see it that works.