Fun with file permissions and server errors

[#1]

Hello
I've (finally) installed Joomla on my CCGI space, and I'm having problems displaying any of the inbuilt graphics (and styles) in it.  I've tried the obvious - typing a known image's full URL into the browser, and I get an error 500 message stating:
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, support@plus.net and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
Am I missing something really obvious?  I've tried setting the image file permissions to the recommended 644, then got desperate and tried 755, which made no difference.  The images are PNGs, and are in a subdirectory under the Joomla directory, which isn't under the cgi-bin directory.
Any help would be greatly appreciated.
Cheers
Jason

[#2]

Did Joomla upload any .htaccess files within your CGI space? I'd be inclined to say that you have a .htaccess file which is using an invalid directive and producing that error. due to the way the CGI platform works, you wouldn't notice this in PHP scripts.

[#3]

Hi Colin
Thanks very much - I had a copy of .htaccess left over from the first time I tried to install it.  I deleted it and everything seems to work!
Thanks again
Regards
Jason