Thanks for your help and ideas.
OK I have tried changing permissions to 777 and 775 with no difference (i.e ticket is raised with no error given, but the attachment is not uploaded).
I created a small script test.php and placed it in my attachments directory. The script simply does <?=getcwd()?>
This can be run at http://support.proxima-software.com/attachments/test.php(http://support.proxima-software.com/attachments/test.php) (It does not appear to require the httpdocs as part of the path so maybe this is the problem ???)
The output shows the full attachment path to be /var/www/vhosts/support.proxima-software.com/httpdocs/attachments which is exactly as specified in the OSTicket admin panel.
The admin panel also has "Allow online attachments upload" checked
Max file size is set to 50000000
Accepted file types are: .doc, .pdf, .txt, .zip, .gz, .tar
This was all working perfectly before the upgrade to the stable release and the upgrade copied everything across fine.
ny more ideas please?
Many thanks
Mike