Since plugin upgrade, this message appears on my contact form (printed in red):
Please make corrections below and try again.
The temporary folder for the attachment field is not writable.
However, I have set permissions in the attachment folder to 0775 and tested the form. Attachments can be sent with no problem, although form is slow to refresh.
There is an .htaccess file in the attachments folder which specifies:
Deny From All
I know that whenever I upgrade the plugin I have to check permissions on the attachments folder, but always before any error messages went away once I did that.