WEP 2 issues with OSX

[#1]

Another issue, that I have only (seemingly) had with Plusnet.
I have a Macbook Pro (late 2009 model) and my girlfriend a more recent one. Pretty much every time the laptops are woken from sleep mode or whatever it is, they lost the connection to the WiFi. If you try to reconnect it asks for the password, but regardless of careful entry, with 'show password' enabled it reports incorrect password.
This issue does not occur with iPhones, iPads, Kindles, Windows PCs.
Any ideas?

[#2]

Forgot to mention. If I reboot the machines, they reconnect automatically.

[#3]

Hi,
Have you got the latest updates for your operating system? I know at some point there was a glitch with the MAC systems.
Chris

[#4]

What version of OS X have you got installed? Also there isn't any encryption called WEP2, maybe you meant WPA2?

[#5]

Yeah wpa2 sorry. I have 10.6 something I think.
I know it must be an OSx issue, just wondered if anyone else had solved it.

[#6]

Well I have Snow Leopard and have never seen this issue before but then I'm not using WPA2 encryption (only WEP 128 - mainly for other device compatibility).
Could you just check a few things for me, to see how things are set up for you. In the System Settings application, in Network, under Airport, click the Advanced button. In the preferred network list, is your Router's wireless name there?
Also in the Keychain application (in Utilities), is there an entry for your wireless network (either in 'login' or 'system')?
And lastly, what router make and version are you using?