You may want to try using these cheatcodes at the Grub Boot Prompt:
nouveau.modeset=0 xdrvr=intel confx
If that doesn't work, try this instead and see what happens:
nvidia-modeset=0 xdrvr=intel confx
You've got a laptop model using what's referred to as Optimus, where the graphics switches between Intel and Nvidia depending on what you're doing.
But, Mepis 11 doesn't support that configuration yet with the stock kernel and drivers. So, that work around should force it to use the Intel graphics driver only (hopefully, anyway).
See this thread for an example of issues some users have with that type of setup (and there may be some newer threads with better solutions around).
Note, that you may want to start a new thread asking about your issues, so that we're not discussing more than one problem in this thread (which was started by someone needing help getting integrated Radeon HD 4200 graphics to work).
Then, perhaps some of our members using laptops with Optimus technology will see it and chime in with solutions they've found works better with Optimus (as updating to a newer kernel and drivers may help out with the issues)
New topic as suggested and thks for helping