Erasing Slurs

I have been working on a piece of music for a long period of time from MS3 to MS4.5. I have not had any problems with 4.5 until today. I brought up the piece of music and made modifications and realized that all my slurs markings had been erased through the sixteen pages. Also, the slurs do not insert like they did in previous versions (see attachments). Is this a problem from other members?