Do you have an issue loading your Admin Panel?
Do you have a web address like : http://www.mysite.com/index.php?/admin/ and when you try to access your Package Manager the site crashes as your url is now : http://www.mysite.com/admin/
This issue is caused due to a change within the .HTACCESS file on your root folder (Location where SE is installed). This change may have happened by accident if you have added any mods to the .HTACCESS file but a lot of the time it can be caused SE itself not setting it correctly.
To fix this, add the following code to you current .HTACCESS file:
Save and upload overwriting the old version to your SE root folder and all the issues should now be fixed.
Also make a backup of any documents changed in-case the changes don’t work correctly you can always revert back.