Well.....carry on pulling your hair out, I've been doing so since last February, much work was done to improve the offline vault experience. The icon problem you mention is the main one that still bothers me, for the few offline vault users we've got, it's tolerable but not nice but I can see you'd be bothered greatly if you were rolling this out to all your users.....just not nice for support.
It's interesting that you can fix it by manually installing the form, I might try that myself but of course it should work properly via the forms library. However, I was reading the V6 SP1 notes the other day and they stated that this problem is still ongoing and they are now talking to MS to try and resolve it.....so I don't believe you can do more than you've already done. Your only recourse would be to push your Symantec account manager and get them to speed up the fix.
Good luck, let us all know how you get on.
Glenn