Can't access fileserver and internet concurrently

I've got a Netgear ADSL 4 port router that has only one connection that goes to a 5 port ASUS gigabit switch. The switch is in another part of the house where all the PCs etc. are. I have 2 PCs and 2 Thecus fileservers connected to the switch. The router is pretty standard with DHCP enabled. If I have the PCs set to ontain an IP address automatically I can acces the internet with no probs but I can't see the fileservers - can't ping them or anything. If I change the PC setup to manually configure the IP (e.g. to 192.168.0.2) I lose internet connectivity completely. Previsouly with manual config of the IP I could access the fileservers but I can't even seem to do that now!

The router IP is 192.168.0.1, the Thecus boxes are 192.168.1.100 and 192.168.1.200 (both static) respectively.

I'm tried all I know (I'm no expert) but I've no clue on where to go with this - it seems like a pretty basic setup and I thought that I could access the fileservers via the switch without the router getting in the way. I'm tearing my hair out so any help would be much appreciated ...............