Following an unsuccessful attempt to open a pdf file sent to me as an attachment (by my daughter, so genuine), being told it was in the wrong format, I now cannot open the 'new' email window.  A message comes up saying an error has occurred opening this message and please try again.  Currently I am unable to send emails, although still receiving them.  How can I resolve this?  I am using Windows Live Mail version 2011, build 15.4.3555.0308

Thank you!