Multi bit wallet not opening for sending bitcoins......

[minad]

  I am in trouble. I bought some bitcoins in 2012 and loaded it in a multi bit wallet and passworded it. I seem to have upgraded to version 0.5.16 later on in  2013 or 14 and now I tried to use the password now  which was clearly written and saved in a textfile and it says " could not decrypt bytes"  

I am lost and would need help. I have read the multi bit section about password, keys etc and still cannot open the wallet.

can someone give a help or am I missing something

thanks