Dlink 2000AP+ & G520+ Latency

Having a real problem with two separate sites, one is 2000AP+, other is 900AP+ , data transfer is EXTREMLY slow. Both using G520+ NIC's. One site has 64 bit WEP anabled, other has 128bit - apart from that they're at defaults.

Latency is terrible - you can wait up to 5 seconds for IE to view another drive on the network. Conecting devices with Cat5 via hub solves the problem immediately - instantaneous access to other devices so it's got to be the Dlink setup. Is there something I'm missing here?

Any assist appreciated