Reconnect fails after standby when using WPA

Hi,

when using WPA (pre-shared passphrase) my laptop fails to reconnect
after standby. Using manual disconnect/reconnect also fails - a reboot
is always required.

The laptop will find the wireless network and indicate a connection
(Speed etc.), but no transmission is possible. I can't ping my router
(which works as the Access Point)

The problem doesn't occur when not using WPA. Also I've not
experienced this problem with other laptops.

The Hardware:
Router (AP): SMCWBR14-G EU
The router is not acting as a DHCP-server, all IP-addresses are
indicated manually.
Laptop: Toshiba Tecra A3 (101)

Thanks in advance
Ryan Dahl