I have several servers and from the entrance Minecraft 1.5 I am flooded with notifications shearing and lags klient ofline and online !!!

I do not have weak computer and every game with great 3D graphics work seamlessly in FHD ! Minecraft lags 5 min the inclusion. Despite the busy between 90/250Mb RAM

I have to change the resolution in the system at the lowest possible that your game has not crashed.
Just use google and read how many new problems with this May people since the introduction of version 1.5, None optifine or other treatments do not give the result only reduce the resolution

I have also to Minecraft mods of 145 in version 1.4.7 which is activated in 2 minutes NO LAG and and is more functional than 1.5 300%