Same problem here
I have the same problem with a new installation of 4.5, all file permissions on 777 and with the temp directory deleted, tried with 2 browsers (IE and Safari). Still get the same error message and a crash:
Warning: simplexml_load_file() [function.simplexml-load-file]: ../../themes/temp_editing/theme_settings.xml:1: parser error : Unsupported encoding windows-1256 in /mnt/web5/43/92/5107192/htdocs/mcnaughtan_de/webassist/plugins/styler/styler.php on line 104
Warning: simplexml_load_file() [function.simplexml-load-file]: <?xml version="1.0" encoding="windows-1256"?> in /mnt/web5/43/92/5107192/htdocs/mcnaughtan_de/webassist/plugins/styler/styler.php on line 104
Warning: simplexml_load_file() [function.simplexml-load-file]: ^ in /mnt/web5/43/92/5107192/htdocs/mcnaughtan_de/webassist/plugins/styler/styler.php on line 104
Fatal error: Call to a member function asXML() on a non-object in /mnt/web5/43/92/5107192/htdocs/mcnaughtan_de/webassist/plugins/styler/styler.php on line 117
So what now?
Further detail: I am now unable to change theme