Problem starting hp-toolbox & hp icon in systray.

Hi! I do not have access to the hp systray icon in Ubuntu 8.04.1 LTS...I'm using a network-attached Photosmart C5180, as far as I can tell, all other facilities of it work (I can both print and scan from my Linux system, as well as all other systems on the network). when I try to start the toolbox or the systray icon manually, I get this error.
daniel@Bedivere:~$ hp-toolbox
error: Unable to open /home/daniel/.hplip/hp-toolbox.lock lock file.
And when I try to start the systray icon manually, I get this:
daniel@Bedivere:~$ hp-systray
error: Unable to open /home/daniel/.hplip/hp-systray.lock lock file.
Thoughts? Am I missing something stupidly obvious? I followed the install guide here, if it helps: http://hplipopensource.com/hplip-web/install/install/index.html