Mac OSx stuck at bootup after update 10.9.4

I am holding a Mac book pro mid 2011. I have upgrade my hard disk from a Toshiba 750gb to a OWS solid state drive recently.

A few days ago, I updated my mbpto 10.9.4 and restarted it without problem. During then, I had a dual screen setup. After the update, I disconnect and reconnect the VGA cable only to find that both my screens were having display problem. There were many lines horizontally across the screen. I disconnected the VGA cable and my Mac works fine after a restart. I was able to use it for another day without problem.

This morning I turned on my mbp without the dual screen. I opened a video streaming. When the video loads my Mac display went crazy and it just freeze. I restarted my mbp a few times trying to watch the video. In the end, my mbp always freeze at bootup. When my mbp starts, I see the grey apple logo with many lines horizontally across the screen. After the apple logo disappear, it went to a total white screen and hung there, and I could hear my fan or CPU running heavily.

I have tried the following methods but nothing works:

1. Pram reset

2. On startup I press and hold option and go to 10.9.3 recovery mode

3. Smc reset

4. Tried to boot from a maverick bootable USB

Please help because there r some very important files in there