It would appear that in version 1.6 (I haven't checked previous versions) that you call the PHP function debug_print_backtrace.
I was running my WordPress 2.5 blog on PHP 4 (because I hadn't gotten around to having my server run .php as PHP5). While running PHP4, I couldn't activate your plugin because it triggered an error on the line with the debug_print_backtrace function. After telling my server to run .php as PHP5 I had no problem activating the plugin.
You might check and see if the function debug_print_backtrace is PHP5 only. If so, you might need to let users know.1: Comment Link
Thanks for that. You are correct debug_print_backtrace is PHP5 only, I will try and get it fixed today.2: Comment Link