I have just been 'rejected' with the laptop wanting to complete a WU. Said it could not find the server etc...
A quick check with the quad confirmed server available
Back on the laptop, I quit folding programme, rebooted & it found server, uploaded completed WU, fetched another on and is as happy as JtP with chrome juggling thingies.
I am not claiming this to be the panacea of all woes but I have noticed that running the computers 24/7, it does the machines good to reboot every couple of days or so, especially if the machine is being multi tasked. I guess rebooting flushes buffers, cache and other dregs left behind and giving it constipation.