Affects 14w04b too.
Screenshot http://i.imgur.com/JPSufPa.png
single and multiplayer Windows Java x64 1.7.0_45
Jemus42 please update: OS irrelevant
I have this issue, all my friends on my server do too. I'm on windows 7, not Mac.
Issue is present in 1.7.2 and 1.7.4. Java 7.0.13 x64
The same tick message is shown in the log. The tick may take up to 3000 ms.
The issue comes sort of randomly, but is connected to certain areas of our built-up world.
Main suspect blocks are large amounts of tall falling water, and glass blocks.
I have resolved the issue for one area by deleting water. But this does happen in one area with no water also. To reproduce, make several pillars of water falling from maxheight.
Seems to be fixed in 14w29b. FPS is smooth all the time in problem areas of my map. (Lots of block placing glitches in my test though. Single player, with a texture pack.)