You cannot detect wdr3600's SSID on your printer automatically and connect to it? To add it manually, did you find out corrent Pin of the printer?

In AP mode, to login 192.168.0.254, you have to assign a static IP, such as 192.168.0.200... Just follow this, http://www.tp-link.com/en/article/?faqid=375.

What's the default gateway on your laptop connected to the new SSID 2? WA801 is using smart IP or static IP?

You know neighbor's password instead of security type, right? 5210G only supports WEP or no security in repeater mode... You may try WEP. You should consult TP-LINK technical support to find a proper...

Maybe TP-LINK_45F138 is your neighbor's network, without security? No big deal...

I heard that to change MTU size can solve such problems... You may try to change it to 1460 or 1400.