Pages is telling me it can't open.

Hi there.

A similar thing has just happened to me. I've had Pages (iWork '09) on my iMac for years and this morning it (and also Numbers is telling me it can't open. I haven't upgraded to Mountain Lion. I may have done a software update with Pages & Numbers in it, but can't honestly remember. It is version 4.3 and looks like it updated 10/12/12. Any ideas?

<Re-Titled By Host>