Hi
Possibly there is a problem assigning the ip address automatically after the notebook has been set to sleep mode. It could be also another reason for that but it’s always difficult to say what could affect the wireless networking…
I think that you should try to update the Wlan driver.
Not sure exactly what Wlan card you have but here you can find all the newest available WLan drivers for Toshiba notebooks:
http://aps2.toshiba-tro.de/wlan/
Uninstall the old driver firstly, after new reboot install the new downloaded driver for the Wlan card which is built in the notebook.