Help my Tekkit wont work

[mr_cookie74]

Hi I can run Tekkit classic on 32 bit java but i keep on running out of memory so i upgraded to 64 bit java and now when i load into my friends world the blocks do not load and i just crash

Any Fixes ?

[AetherPirate]

Open the laucher, click cog wheel upper right corner, the button for the logs is on the lower left after that. Pastebin the most recent one.