I just found this on github and it looks like maybe this is what happened with me also. 

"cspuhler commented 8 months ago: Ok, that's probably it, when I share a wallet on two computers I export the private keys from one wallet and import them to a new wallet on the second computer, so the second computer then has an additional key which the first one doesn't. I guess the way to go around it would be to prompt the user if he wants to import keys when creating a wallet and forego the creation of a new key in this case."

Thanks for acknowledging me anyway.  I've got to get some help.  I've been reading on the internet, listening on podcasts, going to Bitcoin meetups and even started one in my area to try to help myself figure out my questions but I can't seem to understand the nuances enough to know if I'm doing this right.  At one point, in an attempt to secure my BTC I deleted all my hidden multibit files and basically deleted my wallet and all its info with keys, etc.  Thank god I had exported the private keys to a USB stick and an ext hard drive and was able to re-import them and recreate my wallets and account for all my bitcoins.  But then I wanted to move them to a second computer I have that would not go online all the time like I am with my main machine and I had to import the keys again.  It worked again but then this is where I was trying to create a paper wallet and was comparing the private keys to the ones I had exported the two times earlier and they never matched so I am confused and afraid to make another move until I can find a way to be sure my paper wallet is accurate  

Is no one helping me because no one knows how to or no one cares to?

I am new and not very technically savvy.  I have always had a computer since 1987 but have primarily used it for word, excel and the internet. I became interested in Bitcoin after listening to Andreas M. Antonopolous and I want to support this decentralized currency and value transfer system. I want to buy and hold Bitcoin and I want to buy and commerce with Bitcoin.  I understand I should hold my savings of Bitcoin in cold storage - on an offline computer and paper wallet. And I understand I should keep a small amount for commerce on a hot or online computer and/or smart phone.  But before I can begin trying to commerce with Bitcoin I need to understand how to secure my wallets successfully.  I have been getting very confused trying to figure this out though.  I'm using Multibit because I liked the idea of connecting directly with the peer to peer network instead of relying on a third party. I have the latest version Multibit on my Mac OS 10.8.5.  I have generated two wallet files.  The first wallet has two addresses.  The second wallet has one.  All addresses have a small amount of Bitcoin in them. 

Questions:
1) I find that there is no button to click that says backup your wallet and choose a location to back it up to.  It appears to happen automatically in the background but you have to find where the multibit files are - which is in a hidden folder - I figured out.  So, in order to back those files up somewhere else you have to find the hidden location where they are and then copy them to where you'd like them to go.  Is this correct?

2) Exporting private keys. I experienced that Multibit does not recognize my USB stick when I try to export private keys to one. I had to export my private keys to my desktop then copy them over to my USB stick.  Is this right?

3) Finally, yesterday I was trying to create a word document to include each of my wallet file names & passwords as well as each address password and private key so I could put them all together on one word document and print out to keep as my paper wallet.  I had exported my private keys a few times before - once the day before and once a few weeks ago.  This last time I exported them I opened them in TextEdit to compare them to the earlier exports and saw that they didn't match. It looks like a new private key is being generated every time I export a private key. Is this what is happening?  I am now suddenly completely unclear if I have the right private keys printed out and matched to the right addresses and I feel very vulnerable.

Thanks for your help.  Until I can figure this out I'm stuck in my process of helping out with the adoption of BTC.

All the best and the best for All!