Problem with Wireless Disconnects & AP "Association"

I'm having huge problems with my wireless connections from my laptops. One is a Lattitude D600 the other a D800.

I currently have a Belkin F5d7630UK4A ADSL Wireless G Router, and two desktop Pentium III/IV based PC's with PCI Belkin Wireless cards.

Both of my PCI Wireless cards and the cards supplied inside my Dell Laptop's have wiress lan utility applet's. These applet's show you link status, signal strength, etc.

All clients use XP Pro - the desktop PC's SP2, and laptop's SP1.

However, in the Wireless utility applet the desktop PC's show their connection status as being "associated". The laptop's show their connection status as being "Not Associated".

However, both types of connection are working - but I've having more problems with the laptop's at the moment with random disconnects. I was wondering if the two items could be linked?

I guess it would help if I knew the difference between and associated network connection and an unassociated one!

I wasn't sure if the issue of association was linked to the laptop's running XP SP1 (they are work owned laptop's and we aren't allowed to install SP2).

It was only last night I happened to notice that both desktop's were showing a connection status of Associated, and the laptops were saying Not Associated. I don't recall ever seeing the laptop's associated.

I've changed the ssid on the router to a unique value of 'jameskbelkin54g' and I'm using WPA-PSK. On the laptop network authentication is set to WPA-PSK , and data encryption is set to TKIP. With the key entered.

The laptop's do sometimes work completely fine - but again they always seem to say "not associated" - which as these are the machines I'm having problems with random disconnects I'm thinking it is related to the association. Once the laptop loses the connection it goes into an endless loop of (viewing the Wireless utility):

1) The Wireless card connects, with Excellent reception, yet does not have an IP address yet
2) The Wireless card reports the encryption method is TKIP,WEP
3) Sometimes the card will obtain a TCP/IP Address from the router - if it doesn't get an address goto (6)
4) The connection will sometimes start to work
5) The connection will stop working after a few minutes
6) The wireless card reports the IP Address as 0.0.0.0
7) The wiress card reports encryption has changed to TKIP,WEP; Key Absent
8) Windows reports the Wireless connection is unavailable
9) After a few minutes Windows reports the Wireless connection is available again... and whole of the above sequence begins again.

Could it be an issue with using WPA-PSK? Are there issues with Windows XP SP1 using WPA-PSK?

I'm sure it's a configuration issue, I just wish I could work out what's going wrong!