TPP GUI error message: sh: tpp_hostname: com mand not found

[Eliza]

When trying to use the TPP GUI the webserver error log is filled with
the following error message:

[Fri Jan 08 14:01:42 2010] [error] [client xxx.xxx.xx.xx] sh:
tpp_hostname: command not found, referer:
http://localhost/tpp/cgi-bin/tpp_gui.pl?Action=display&page=filebrowser

I am also seeing the same error message in the GUI:

Unable to access xml file via webserver, so cannot check xml file for
changes ()
Check webserver configuration if desired.
(URL: undefined)

Debian Etch TPP version 4.3. Suggestions on how to fix this?