I am pretty sure that the version of synaptic you have installed is actually 0.75, even though the about box says 0.70. I can't check my system right now because I'm not in front of it, but I think mine says the same thing.
There are no bugs listed for this version mismatch, but looking through previous bug reports, it looks like synaptic has a long history of
displaying the wrong version numbers in the about box.
AMD Athlon II X4 630, 4 GB DDR3 RAM, Nvidia GeForce GT 430 - 64-bit LMDE (Gnome3) tracking testing, 64-bit Archlinux, 32-bit Windows XP
Aluminum Unibody MacBook - MacOS X 10.7 "Lion"