all was working until i joined plusnet

[#1]

after a terrible start to my contract with plusnet I now find that all my pcs connect to the internet but they don't connect to each other.
they are all wireless connections.
e.g I used to be able to print from my laptop to the printer attached to upstairs pc, now it doesn't even see the pc or printer. all pcs can ping the router and the router can see all the wireless connections but they cant see each other. the ONLY thing which has changed is the addition of the new router from plusnet
help from any network gurus out there please 
thanks in advance

[#2]

It's possible that your old router used a different IP subnet to the the Plusnet one. If this is the case then you need to check that any firewalls on the Pcs are configured to allow traffic on the new subnet and that any printer ports (used for network printer access) are changed for the new ip/subnet (http://www.region1tech.umd.edu/faq/Printer_Ports.htm )
Hope that helps

[#3]

You could try using your old router but with your new Plusnet Username/Password.
Keep the Plusnet router as a spare.