If you think the problem is in the browser, then you should determine what data the browser received and determine why that's making it hang.

However, it's much more likely that the browser is hanging because it didn't receive an answer. Therefore, I was asking "Where in your script does it hang?"

Well, I went and ran the script by telnet to get all the output. There was one line with a missing semim-colon. Fixed it, but made no difference.

Problem is that to run properly, it needs a couple of form values plus the .htaccess username out of $ENV{'REMOTE_USER'}, so I can't get it to run completely via telnet - or at least if it's possible, I don't know how.

CGI (the module) scripts can be run be from the prompt. See the "DEBUGGING" section.

Or you could add statements that print the script's progress to a log. Don't forget to (auto-)flush.