[imp] POP and dreaded Thread link?

[...]

Hi folks.

Ugly problem here.
    Client logs in under POP

The dreaded "Thread" link appears above the message link.
Mr. Clicky clicks the link "Thread"

Boom!
"Warning: imap_thread returned an emtpy tree..."

Then client can not check their email forever after.

Each time client logs out and logs in they see this message spotted through
the inbox (sans messages).

Ideas?


Best Wishes,

Jim