Help please!

Everytime I open a new document or an existing document i cannot modify it.
At the bottom of the page a message comes up saying "This modification is not
allowed because the document is locked"
I've tried a virus scan and the scan reported nothing, and I've also checked
properties to see if the documents were under "read only" and they're not.
Could you please help, as I don't know what else it could be?

Thank you, Amy