Here is a link to a .bat file i made which stop the 1.8.1 bug error [the link is at the bottom near world save]

All you have to do is change the drive location in the .bat file [i.e. go in it and edit it] And once your inside it, you will see a soem text that says C:computerusersdeclandesktopminecraft.exe You need to change that to so it leads to the location of where you minecraft.exe is [mine being my desktop]

Once you have done that, you can change the amount of RAM you give your minecraft, mine says 4052 i think change both of the numbers that end in mb to the amount of MegaBytes you want your minecraft say if you want 1gb of ram, you must change both the numbers to 1024mb CAUTION, DO NOT ENTER A NUMBER THAT YOU DONT HAVE THE CAPABILTY OF RUNNING, Say you have 4gb of ram, dont put 4gb of ram for minecraft otherwise your computer will crash and dont put anything higher than 3/4's of the number of ram you have or it will crash!

This can also be used to just allocate more RAM to Minecraft!

Hope its of use!

Declan