Outlook with IMAP account, not downloading complete emails as configured

I have a google-hosted account, connected via IMAP to a fully patched Outlook 2007 installation running on a fully patched XP machine (all 32-bit). I have a bunch of labels/folders, with some of them configured to "download headers only", and the others configured to "download complete item with attachments". The main Inbox is in the latter group. Yet when new emails arrive, they don't always fully download. After clicking on those emails, the rest of it downloads, but the computer this is on is not connected via a very quick Internet connection, and it can and does take 20-120 seconds to finally display some emails, and it feels a lot longer than that.

Anyway, this is a new IMAP connection configured with a brand-new (created on Saturday) Outlook profile.

I was using the "Google Apps Sync" utility along with the google account, but I kept getting tons and tons of sync errors, so I had to switch to an IMAP account for email, and I'm trying out a few different options to sync the calendars and contacts. So if someone has a solution for the Google Apps Sync sync errors (unfortunately the errors were all "Generic" errors, so I never could figure out what the problem was - I opened a support ticket with Google support but thus far I haven't heard back from them after sending them the trace and log files they asked for).