Asio time usage overload - please help!

Hello, i am using cubase 5.1. 32bt on a 64bit windows 7 system.
My PC configuration is:
Intel i7-4770K 3.50ghz
16gb of RAM
I have 10GB free on my C drive and 60gb free on my D drive - where cubase is installed with all my plugins.
My sound card is M-audio fast track ultra and i am using 128 asio buffer size and 44.1khz sample rate.
Increasing buffer size or sample rate when mixing doesn’t help.

I am having trouble mixing because my asio time usage overloads and my cubase freezes. I’ve got a lot of plugins in channels obviously and I know that 32bit cubase only allows 4gb ram usage but when I open task manager, it shows that cubase is only using about 2gb of memory so I am confused why my PC chokes with asio time usage.
Please help, i don’t know where the problem lies.
Thank You in advance! :frowning: