Getting 'undefined index: 0' on celltypes/file.php

Edit Subject

Hi. I have a matrix which allows me to add up to 18 images. Adding the first image works fine, but when I click 'add file' thereafter, my file manager window pops up and I see the attached screen.



Two problems:

1. Although ‘upload file’ is selected by default, no option to upload presents itself. I have to select a folder, then reselect upload to get them to reappear.

2. If I select an image from the thumbnails you see on the screen, it allows me to save it and all looks well, until I hit the front end where I get this little lot:

a php error was encountered
severity: notice
message: undefined index: 0
filename: celltypes/file.php
line number: 182

a php error was encountered
severity: notice
message: undefined index: 0
filename: celltypes/file.php
line number: 182

a php error was encountered
severity: warning
message: cannot modify header information - headers already sent by (output started at /users/andy/sites/spaces42/_system/codeigniter/system/core/exceptions.php:166)
filename: core/common.php
line number: 428

This is using EE 2.1 with Safari 5 on OSX.