include/common.php is included several times....

Now there's a test in mainfile.php to prevent this, and it actually doesn't happen in normal cases (I normally test protector compatibility before doing releases).

I could have made a mistake, but here I think more that the cause is coming from a badly edited mainfile.php (the include lines for protector and common.php may have been moved out of the if ( !defined("XOOPS_MAINFILE_INCLUDED") ) { clause).

You may want to change the include line like this, it should fix the problem: