Question: Just tried Safari (got advised to save battery power over Chrome) and the "Save As" button is disabled!
Can't save a single page!

Any idea why this happens and what I can do against it?
Thanks!

EDIT. Safari version 6.1, MacOS 10.8.5

Answer: 
Ok, I found it - it does not let me save page until it is fully loaded! 
Which is painfully slow sometimes, comparing to Chrome.
As far as I can see, Chrome still lets me save page even if it is not complete and even when I just started loading it still works with previous page!
So I can still save the previous page after mistakenly clicking on a link.
I'm not sure on the *why* but if you use `Cmd`+`S`, the **Export** dialog pops up as expected (After that, **Save As...** is once again available. Until you reload the page).

I think it's a bug in Safari (I base this on the fact that it's also possible to reactivate **Save As...** by mousing over it in the menu, closing the menu and then reopening it again...)