iPhone4 email - read/unread and preview issue

i've been having intermittent problems with email on my new iphone. i have it synced with gmail and set to display 2 preview lines. the problem is that sometimes it stops showing the preview lines on new messages. further more, if i open and view the message, the inbox will still have a blue dot denoting that it has not been read, even though the mail icon shows no new messages.

has anyone seen anything like this? it seems to stop if i restart the phone or play around with the settings, but invariably it comes back.

thanks.

 

i've also noticed that when i'm in the inbox and i swipe to delete it ends up archived in my all mail section. i've made sure that i turned off that feature, yet emails still end up there rather than in the trash, as with my previous iphone 3g.