In my case, I got the double foul. My NAS tried to mount forever and failed; same with a Windows 8 PC on my network. The cause appears to be changes made in the networking stack made by Apple. Apple's SMB2 implementation doesn't work with a lot of SMB2 devices -- even networked drives from Windows machines. [SMB2 is actually used by Mavericks for Mac-to-Mac connectivity, unlike older versions of OS X where AFP was the default. –Ed.]
One easy fix involves changing a little bit of text in your server connection URL. Here's how it works: In the Finder, choose the "Go" menu and select "Connect to Server..." (command-K). Type "cifs://yourservername" and hit Return; the server should mount.
Did Mavericks kill your SMB network drive access? Here's a fix | TUAW - The Unofficial Apple Weblog