Mail todos consistently lose their link to messages and notes

Question

Mail has this real nice feature of linking todos to messages and notes,
so I can jump directly from an iCal todo to the corresponding email message.
However, Mail consistently loses those links:
The todo is still there,
the message is still there,
but the two are not linked any more.
Sometimes, the todos are duplicated:
one still has the link, but doesn't appear in iCal (only in Mail),
the other appears in both in Mail and iCal, but has no link.
I have the suspicion that this occurs when I sync with iPod and/or MobileMe.
Any ideas?

Answer 1

I have the same issue with Mail 4.x on Mac OS X 10.6.2, although I am not synching with iPod or MobileMe.
I've tested different options thoroughly. I first had MobileMe setup as an IMAP account, and in Preferences elected to store new notes and 'to do' items in the MobileMe account. This *did not* correct the issue of disappearing links, though it did create difficulty working with 'to do's otherwise. Specifically:
1) new 'to do's consequently could not be assigned to local iCal calendars, and instead required I create (or recreate) my calendars on the MobileMe IMAP server;
2) calendars created on an IMAP server can not contain events and may only contain 'to do's (according to iCal), thus requiring that I maintain two different sets of calendars if choosing to store notes and 'to do's on an IMAP server such as MobileMe;
3) within the Bento 3.x application (which I use to associate 'to do's, email and notes with address book contacts) the new 'to do's appear without any associated calendar because Bento can not read calendar data from an IMAP server—associating a local calendar with the 'to do' from within Bento causes the 'to do' to be stored 'On My Mac.'
I thus have elected to store new notes and to do items 'On My Mac' which, I understand, may not be a reasonable solution for most people using multiple devices—but at least doing so avoids the above issues. It does however create a conflicting issue:
4) if you need to link a 'to do' to an email as opposed to a note, either the 'to do' is required to be stored on the IMAP server (despite the option in Preferences) and thus causes the issues above or, following the inference made within "Mail's Help: Creating to-do items," you need to setup your email account access as POP and not IMAP so that your "account" is also 'On My Mac.' This is obviously not ideal.
Another observation when storing notes and 'to do' items 'On My Mac' is that the links created seem to be lost only when you quit and restart Mail; the links remain intact as long as Mail is running.
Does anyone else have further comments or ideas?