Thanks for posting the screenshots and urls - they helped me diagnose this problem.
By replacing the code parameter with "a" characters and testing different lengths I was able to determine there is a configuration problem in your Apache server that is preventing this from working. OAuth works by passing long unguessable tokens around, so it requires very long url parameters.
You can see the problem is reflected by different error message responses from these 2 urls:
Not working
Working
I googled this problem for you and this is the most likely answer:
http://www.php.net/manual/en/reserved.variables.get.php#101469
Cheers, Damyon