Mint freezes just after boot

[avdmys]

I installed linux mint 13 two days ago.
i have acer aspire 5750G with 4Gb ram, i5 second gen, 1GB nvidia graphic card and dual boot win and linux.

I had two major problems:
1)The brightness control doesn't work by default so, i added GRUB_CMDLINE_LINUX_DEFAULT="acpi_backlight=vendor quiet splash " on to file /etc/default/grub.
2)The nvidia card heats up a lot taking the battery life from 3 hrs 45 min to 1hr 10min. so, the solution i found was:
echo ON > /sys/kernel/debug/vgaswitcheroo/switch
echo IGD > /sys/kernel/debug/vgaswitcheroo/switch
echo OFF > /sys/kernel/debug/vgaswitcheroo/switch

running these three lines on startup stops the heating improving the battery life to 3hrs 30 min. i made a script and added it to /etc/rc.local file.

I informed about the above problems because i have made the changes to boot.
The current problem is every time i boot into linux mint it just freezes completely as soon as desktop appears. I hold power button to turn off. Initially two or three time it used to boot but now its not (it used to boot even after the changes were made).

i am not very good at linux so please bare with me and i forgot to inform i used to use ubuntu12.04 before i installed mint.

[cwsnyder]

echo ON > /sys/kernel/debug/vgaswitcheroo/switch
echo IGD > /sys/kernel/debug/vgaswitcheroo/switch
echo OFF > /sys/kernel/debug/vgaswitcheroo/switch
These three lines should normally only need to run once, not every time you restart.

Can you get to command line by pressing the Ctrl-Alt-F1 and come back to your desktop by pressing Ctrl-Alt-F7?

[avdmys]

Thanks for the reply cwsnyder.

The three lines need to be run every time. I have tried but when i run these lines and boot again everything is reset and need to run the lines again.

Nothing responds. keyboard,mouse,touchpad wont respond, everything is frozen. I have tried pressing ctrl+alt+f1 no response.
But initially for two or three secs touchpad does work and then hangs.

[avdmys]

someone plz reply.
is there anything that can even be done about this problem?
i feel we dont know what is the exact problem (cause of the problem). is there a way to find??
plz do reply ,thanks.

[a3lt]

Did you figure anything out? I think I have the same problem as you did...