Oh ok, thanks man, my PC has 12GB and I allocate 10ish to most games and it works fine (even different modpack launchers). Wierd but I lowered the memory and its working!
So when I go to launch a new modpack it gets to 'loading assets' and then just stops and does nothing. I have 64 bit java and 12GB ram and I cant figure it out.
Here's a link to my logs: https://pastebin.com/VnS9Z80h