Outlook appt start times wrong

[Guest chucky.egg]

OK, I had this issue before but it just got worse.

The GF has a 1&1 POP3 mailbox. I (now) have a Sherweb Exchange account.

When she sends me a meeting invite [don't laugh, it's the only way I stay organised] the time is correct. but when she sends me an All Day invite the start time and end time are 5 hours late. So an All Day appt starts at 5am and ends at 5am the following day.

I've checked both our laptop dates and times, and the time zones match. I've looked at my Exchange regional settings and they match too (GMT on all).

Any ideas where the problem is, or better yet how to fix it?