Back up to Time Capsule failing

Hi there,

I have been making repeated attempts to back-up my Mac to my Airport Extreme Time Capsule with no luck.

I have been successful in backing-up to another external hard drive but wanted to have 2 back-ups and my Time Capsule was purchase for that specific reason. It seems that the Mac is no longer recognising the Drive and I have tried both a reset and Factory default reset. On both occasions, the Time Capsule seems to re-start and resume with it's old settings. I am also getting this error message when the Back-Up fails.