wp-signup.php is properly loading, but on submit the form doesn't process and instead tries to have me download a blank wp-signup.php file.
I've tried re-uploading wp-signup.php and I've checked and it has the same permissions as every other file in the install directory.
This is on a OS-X server with apache.
anything in your apache error logs.
No mention what so ever of wp-signup.php in the error log. The access logs show :
xx.xxx.xx.xxx - - [10/Jul/2009:14:06:40 -0700] "GET /wp-signup.php?new=testingtest HTTP/1.1" 200 4408
I just upgraded to 2.8.1 though the issue persists.
The errors in the logs may be affecting the signup page, but not showing wp-signup in the line itself. Because it lists where the error starts.
What plugisn are you running that hook into wp-signup?
No plugins are currently activated and there are no entries in the error log for multiple minutes surrounding the request.