Whenever I play Minecraft, it is really laggy ever since I updated it to 1.4.5

Put the summary of the bug you're having here

I thought that it would be really fun and not laggy as normal.

The game became SUPER laggy and I could move but it always glitched me out. I know its not my computer because it is very powerful and I even tried uninstalling things but it still didn't work.

*Steps to Reproduce:
1. Start Minecraft
2. Load World