Is it my CPU?

Still trying to make this work and failing.

I upgraded my RAM after getting the FAIL message on the 18th to 18Gig
I then tried to mine again, my computer froze after making the DAG file and got an error saying not enough space on drive "There is only 13.3MB free on this drive." So I went out and got a 2T HDD.

This is my current setup:

Motherboard: ASROCK H61 PRO BTC
CPU: Intel Celeron 2.66Ghz
RAM 18G PNY
GPU: XFX RX480 GTR 8G OTC
OS Ubuntu 14.04

My version of Geth is the new one posted two days ago.

I run Geth and let it sync, then I run Ethminer. I get to:

[OPENCL]:Creating buffer for header
[OPENCL]:Creating buffer 0
[OPENCL]:Creating buffer 1

If I'm lucky, 1 out of 3 reboots and trys I will get "Working on block#XXXXXXX" but then the computer freezes! It's won't mine and I get this error for Ethereumpool.co:

Miner statistics

0XCB49E61D5D85198B002CDE45C4AB46A0DD12FDCD
HTTPS://ETHERCHAIN.ORG/ACCOUNT/0XCB49E61D5D85198B002CDE45C4AB46A0DD12FDCD
0.00 MHASH/S
0.00 GHASH/S
0 ETHER
0 WEI

MINER IS INACTIVE
or
It seems your ethminer does NOT have function called eth_submithashrate. To get valid and reliable statistics please update your ethminer to lastest version. This affects only statistics, it does NOT affect revenue! If you have any concerns please feel free to contact us.

The only thing I can think of is that the CPU is not fast enough but I want to KNOW before I spend any more money trying to rectify the problem. Please help if you can.

Thanks!