Cubase 5.1 will not open

I have been working on projects for the last 3 weeks and they have been working fine. Today I went to open up my latest project and it would not open. I initially had a message concerning elicense. I updated my elicense and now any cubase projects I have created in the last two years will not open… BUT any projects created over two years ago open fine.

I am on a PC with windows xp 32 bit. and running through a MR816x.

Please help!