cannot create New Record (icons greyed out)

Hi

I am still pretty new to Access and had a form that worked fine until Friday
when it disappeared in Form View. Over the weekend it seemed to resolve
itself and reappeared - but... I cannot now add a new record.

I am using Access 2007. All the icons on the Records section of the Home tab
are greyed out apart from Refresh All. I had a go at creating an Add New
Record button - just to see what happened. When I click this, I get the error
message " You cannot go to the specified record".

I have gone to Design View and looked at the various properties but nothing
seems to suggest that I can't add/ edit anything.

Any ideas gratefully received!