BB Curve 8900 :: SMS Deleted Not Low On Memory

Ive only had my Curve 8900 for about a year, and I know thats about a decade in techie years but still...I'm incredibly frustrated with the issues I've been having!
Most pressing of these issues is that my phone keeps deleting my SMS even though my memory is NOT low! I've read tons of posts about the same issue but its always resolved by freeing up some memory.

My current memory status:File Free: 90317537

Thus I have 90.31 MB free...yes? Shouldnt that be enough?

Apparently not. I have nothing stored on my blackberry, everything is on the Media Card (4GB) and I only have a couple applications (MSN, Facebook, GTalk) and yet my SMS get deleted regularly unless they are saved on my SIM card and also notifications on facebook are often deleted (those dont matter too much to me but I believe it is resulting from the same thing that is deleting my SMS)

Further, my call logs ARENT being deleted. So I dont think its the same memory problem everyone else seems to have. I will be most most most grateful to anyone who can help me out here or at least point me in the right direction.Im seriously considering shelling out for an iphone even though ive only had my blackberry for a year because I do rely heavily on smartphones and losing SMS is really driving me crazy. Sometimes I cant even read a newly received SMS before its deleted! By the time i pick up my phone its gone...

Ive had other problems as well, not to ramble on but in case they are related:
I will be chatting on bbm for example and it will just exit out of the conversation or the application entirely. Oftentimes it slows down so much that the minute hand or whatever stays and everything freezes until i do a battery pull (which i hate doing but have to at least once a day) This often happens when Im using the browser...Sometimes when I am getting a call the minute hand appears again and I cant answer Oftentimes when this happens it says that I am receiving a call from an unknown number, but when they call back it turns out its a number i have saved...weird...

Sometimes I cannot dial or call (frustrating as hell when i need to make a call urgently!) I have to again do a battery pull to fix the issue. Ive had other issues here and there but nothing really worth mentioning after this long rant so I'll just leave it at that!!
Thanks to whoever has had the patience to read all this and I really do hope I can get some help before I release my frustrations on this piece of junk and end up having to spend tons of money on another brick...