Connection not working after XP sleeps

I just installed a wireless router (D-Link DI-524). We have only one
computer, a laptop, running XP Home with SP2 installed. After installing the
router, there are times when the connection does not work:

1. After XP goes to sleep.
2. When switching between the wired connection and using the external
wireless card.

Restarting windows always solves the problem but that's kind of annoying.
The icon in the system tray always shows a working connection whether wired
or wireless but when using Explorer or Outlook Express they don't receive any
data.

Any help would be great!!