Using Windows XP SP3, updated drivers yesterday, "Belkin Wireless G+ MIMO" or something router + adapters.
But specifically:
When the Encryption says enabled, the network connects fine.

When it's disabled it's a hassle to get it to enabled. In the connection Properties (right click in Network Connections, Properties), it's configured to connect to the right network, and uses WPA2-PSK (with key loaded) and AES encryption.
Repairing the connection is 100% hit and miss with it sometimes choosing Enabled, and working, and sometimes Disabled.
Is there anything specific I can look for that would ensure encryption is on, instead of it randomly choosing Disabled?