We have a dozen or so HTC Trophy users around the business, all on Vodafone. Most of them, including me, have encountered a problem with the phone reporting a SIM error and not making or receiving calls, texts or email syncing. Restarting the phone fixes the issue, but as it can take an hour or two to notice, users can miss quite a few calls and texts.
The problem seems to be more frequent on phones that have the Mango update. It is intermittant, it doesn't usually happen more than once a day, and can be up to a fortnite between occurrances. Its not limited to an area - its happened to me both in Hamilton and in Auckland.
I haven't seen any mention of it online from other Trophy users, and our Vodafone rep hadn't heard of anything - all he could recommend was a SIM swap, which seems an unlikely fix for a problem affecting most of our Trophy users, and none of our other smartphone users.