Ok, I was a bit daring and turned display errors on. Got the following.
--------------------------
Warning: Cannot modify header information - headers already sent by (output started at /home/myusername/public_html/wp-inst/wp-admin/wpmu-edit.php:2) in /home/myusername/public_html/wp-inst/wp-includes/wpmu-functions.php on line 73
Warning: Cannot modify header information - headers already sent by (output started at /home/myusername/public_html/wp-inst/wp-admin/wpmu-edit.php:2) in /home/myusername/public_html/wp-inst/wp-includes/wpmu-functions.php on line 74
Warning: Cannot modify header information - headers already sent by (output started at /home/myusername/public_html/wp-inst/wp-admin/wpmu-edit.php:2) in /home/myusername/public_html/wp-inst/wp-includes/wpmu-functions.php on line 75
Notice: Undefined index: id in /home/myusername/public_html/wp-inst/wp-admin/wpmu-edit.php on line 39
Notice: Undefined index: id in /home/myusername/public_html/wp-inst/wp-admin/wpmu-edit.php on line 40
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 72
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined offset: 1 in /home/myusername/public_html/wp-inst/wp-includes/theme.php on line 78
Notice: Undefined variable: allowed_themes in /home/myusername/public_html/wp-inst/wp-admin/wpmu-edit.php on line 288
Warning: Cannot modify header information - headers already sent by (output started at /home/myusername/public_html/wp-inst/wp-admin/wpmu-edit.php:2) in /home/myusername/public_html/wp-inst/wp-admin/wpmu-edit.php on line 290
--------------------