First of all, make sure they're in the right folders. PSPRadio (Make sure it's the latest version from
http://pspradio.sf.net/) goes in the GAME340 folder.
Pimpstreamer should go in your GAME or GAME340 folder (Delete the one in GAME150)
You also have to remember that Pimpstreamer will only work with WPA on firmware 3.10 OE.
If that all fails, try formatting your memory stick. Might help you out.
Hope that helps you!
EDIT: Oh, and you have made sure your network settings were right in the internet browser, right?