Strange problem; programs won't open with wifi enabled

Hi there

I'm running a Dell Inspiron 6000 laptop with Centrino & Intel Pro/Wireless
2200 802.11b/g wireless.

The other computer is a Medion desktop (one of the later ones) with an
inbuilt PRISM 802.11g adaptor (although it does do 802.11b as well).

Got them set up just on an ad-hoc connection - all is well (file sharing,
printers, internet sharing - everything), connected with maximum signal; 54
Mbps - however...

I can start up both computers with the wireless disabled and all is well,
but as soon as the wireless is enabled, on at least one of the computers NO
programs will open (IE, Winzip, games - anything). Any network response on
open programs goes too. But any non-network open programs continue to work
fine (typing on word, start menu works fine etc.)

However, after waiting for about 5 minutes all the programs I might have
told it to open before will all open at once, and full connectivity is back.

Help!

Thanks in advance

Andrew