Open modules/Downloads/admin/index.php and if your nuke is 7.5 7.6 admin/modules/download

in the funtion downloads where it says.... // Add a New Download to Database and around line 197 where it says " . _FILEURL . "

to the right of maxlength="100" change to 255

in the funtion DownloadsModDownload and around line 341 where it says " . _PAGEURL . ".

to the right of maxlength="100" change to 255

then go to your data base and check the structure of the table call nuke_downloads_downloads and under url varchar(100) change it to 255

now you can make your url's up to 255 digits