Rated 5 out of 5 stars

For the last couple of days Ver 3.0.2 is not functioning. It lists the different available formats as before, but Firefox then downloads only a few bytes – 16 or 26bytes - nothing is written to the directory.
Otherwise & until now, CYtS would be my goto plugin for Yt download functionality. So, rated 5.
Anyone else experiencing this aberrant behaviour?

And now, 2012-08-21, I update the above with the advice that this issue be parked meantime. I've disabled CYS (latest version), disabled recently-installed Ghostery (latest version) gone back to FFv14 (latest version), (had been on beta release channel FF15 with auto-updates) ..... all to no avail on this Toshiba W7 64bit.
I did however then discover I was also experiencing the same issue with DownloadHelper 4.9.9. So - I reckon it's some problem on my laptop with FF's downloading.
Other machines here running XP & Vista Business are experiencing no CTS issues whatsoever.

And now updating again - Aug 22nd, @ 10.05am GMT, problem solved. Did as cg-addons (Developer) advised, deleted all youtube cookies and can again now download with no problems. Thanks for the hint..!!

This review is for a previous version of the add-on (3.0.2.1-signed). 

Thank you for your fair review! I am not able to confirm any problem on Firefox 14.0.1 or SeaMonkey 2.11., downloads/conversions are working perfectly from where I am. There may be sporadic problems with YT, it happens. Video file corruption would affect one file (one particular video format for a particular YT video), YT database corruption may affect several videos/files, or server outage may affect users in a geographical area, as a load-balancing server might drop out without the system realizing it immediately. For us to be able to help you more specifically, please, send us an email with more specific information, i.e. YT video(s) affected, CYS version, FFox version.