The first thing to check is that you don't have From Current Time checked in the Preview panel. If you do, and the current-time indicator is at the end of the composition or outside the work area, then you'll get that message.
Next, try restarting and then previewing.
Does this happen with any composition? Does it just happen with one composition? If it just happens with just one, then what are the characteristics of that composition?
Tell us more about your computer system and what kinds of footage you are using.
Regarding the automatic updates: If you don't want to use the automatic updater, then you can manually download the recent updates and install them yourself.
I really don't think it has anything to do with codecs or your firewall. First, like todd says, make sure the current time indicator is not at the end of the composition in case you have 'from current frame' checked in the preview panel. Second, you might want to check the preferences if multiprocessing is on and if it is, make sure the control slider is not set all the way to 'faster rendering'. Third, you can try reducing the ram preview resolution to maybe third or quarter resolution in case your comp is large and complicated. Fourth, you can get more memory for your machine if your project contains very high resolution footage or pictures. Lastly, though it is not recommended, in the secret preferences options turn on disable layer cache, it works for me if i have a large and complicated composition.