the next day, iPoker would not work again, and changing the MTU setting to 1500 again cured this problem.
MTU Settings can be changed by logging into your router"s IP address
http://192.168.1.1 on most routers with your username and password.
If username and passwords are unknown, try the following defaults;
D-Link and Linksys Routers - username: admin and password: admin
Linksys routers are pre-set to 1500 by default and should be OK. Apparently even some of the newest D-Link ones though are 1400 but they can be changed.
Netgear - username: admin and password: password
According to some of my geeky / techy forums, some Netgear Routers that are set at 1458 by default cannot be changed for some reason.
Belkin - username: admin or default and password: admin or password
Speedtouch - username: Administrator and password: leave blank and click OK