Im new to ubuntu, it is the second time i have installed it.
This comp is Dell studio 1558. some specs: CPU- intel core i7 Q720 1.6GHz, GPU- ATI Mobility Radeon HD 5400

FGLRX- i've fallowed these instructions among inspecting many others, i have tried all of the variants mentioned in that tread before reverting back to the drivers supplied with Ubuntu ( through additional drivers ) which apparently seem to work best.
i am testing them with minecraft as silly as it may sound. in 2 to 60 minutes the FPS drop from 70+ to somewhere between 0 and 5.
while "fgl_glxgears" runs at between 400 and 800 FPS smoothly..

I am using oracle ( sun ) JRE6 to run minecraft, i have gotten it through a tutorial linked on oracle's website, i currently have no other version of java installed ( was worse when i had a few others here ).
after closing the game Ubuntu is similarly slow, i've checked the CPU load using System Monitor and it shows one of the CPU's jumping to 80%~100% load at a time.. a reboot solves it.

i realize my mess is up to me to solve but a hand is always appreciated.
tyvm in advance.