If I turn on debug then I get the following "errors":
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 273
Warning: fopen(/cache/adminmenu.php): failed to open stream: Permission denied in file /include/cp_functions.php line 417 Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 367
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 367
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 367
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 367
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 367
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 367
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 367
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 367
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 367
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 367
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 367
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 367
Notice: Only variables should be assigned by reference in file /modules/system/admin/modulesadmin/main.php line 485
With php debugging on, my site gives a white page - only admin site works