recently i have update my XOOPS from 2.0.13.2 to XOOPS 2.0.15
but nothing works anymore, I found this error on the main page
Notice: Only variable references should be returned by reference in file /kernel/module.php line 124
waht should i do?

That notice isn't the cause of 'nothing works anymore'. You need to explain better to us what exactly doesn;t work. Do you have a total blank page? Have you checked the FAQ on blank pages? Have you done a check of all files to see that everything ftp'd correctly? Have you followed all the installation steps including frameworks and did you also get the version with the fixed file 'form.php' as that did cause problems in the initial release? update for the package here If you can be more specific about what doesn;t work and what you have tried we may be able to help.