Mail problems

My aol mail account was working perfectly with my August 2010 13" MacBook pro until lion, and with the new OS it now won't receive messages or send them easily. In the very beginning of lion it was actually running its best (but then again I only downloaded lion 2-3 weeks ago, so that's the time I am referencing) about a week ago I went to open up the mail app on my MacBook and it would not load, and wouldn't since then. On my 3rd gen iPod touch and on the aol.com site, however mail works perfectly. Also, gmail won't let me delete my archived messages through the mail app and I haven't tried on the gmail site yet. This started occurring about a week before I downloaded lion. Please help. Thanks