WowAce

After the TBC Anniversary preptach launched I've been encountering a bug that keeps enabling "Block Trades" on all my characters. After a quick search today I found out it's Postal doing it. Tested it on several characters to confirm. Please make a fix for this, been using the addon for ages and I really like it and want to continue using it!

 FYI it is Postal (which is incredibly annoying that it's on by default and not even at boot-time), but mercifully there's a setting option to disable blocktrade.  There's a tiny button in the top right corner of the mailbox menu to click.  If you have an addon like TSM4, it covers that options button but i was able to click the very edge of the button.  Would have been nice if they provided an addons settings menu like most other addons, or additional ways of accessing the settings menu in case of conflicts like this, but there it is.

Also had this problem start to appear. though thankfully you can solve this yourself.
Just like BlackDahlia1147 described you can change the settings in the mail window. Remember to disable TSM while you do this otherwise the button is hidden.
In the drop down menu disable the TradeBlock and go to Profile and save it as default. This way you won't have to do this manually on all characters.