Linux checkbox - GRUB isnt installed to MBR/bootsector


Today my Ubuntu froze while running Firefox and a re-boot failed to bring up Ubuntu on my dual-boot machine so I am trying to debug. My system was installed last January (first Windows 7, then a Ubuntu install) and has not been altered since and has never previously failed to reboot.

Following the BIOS, my normal boot process first brings up the Windows 7 boot manager (as set by EasyBCD 2.0) with a Windows or Linux (default) selection. The latter choice then brings up a GRUB selection screen, using a separate boot partition (/dev/sda3) _not_ directory /boot of the Ubuntu root partition. Currently I still do get the Windows boot manager and if "Windows" is selected then Windows runs successfully. But if "Linux" is chosen then I just get a blank screen with a blinking cursor instead of GRUB.

I used EasyBCD to look at "View Settings" which gave as choice 2 "Name: Linux BCD ID:frowning:default) Drive: C:\ Bootloader Path: \NST\nst_linux.mbr". But I can't seem to find any more detailed info as to what settings that actually uses.

It occurred to me rather than trying to spend time trying to determine what the current Linux settings are, a good simple test would be to simply add an additional new choice and see if that works. I attempted to do that using "Add New Entry" with "Type: GRUB (legacy)" and "Device: Partititon 3 (102 MiB)" which I know is the Linux boot partition. But I have no idea what to do with the "GRUB isn't installed to MBR/bootsector" checkbox! And I'm afraid that if I make the wrong choice I will make things worse! I can't seem to find any info on that checkbox selection in the documentation or FAQ or via a search of this forum so would greatly appreciate some feedback.
Firstly EasyBCD 2.1 is released, and that checkbox doesn't say that anymore.
It needs to be ticked if Linux is on a different HDD to the boot device.
Are you sure your Linux is on legacy grub ?
Grub2 became the default some time ago.
This is all mentioned in the sticky.
Thanks for the additional info. Didn't really know if I had GRUB or GRUB2 (Ubuntu simply says "GRUB") but since the install was this January went and used GRUB2 and that did give me my Ubuntu back! (after working on this for 8 hours!) At least next time I will know what to do (and also that several things like my DPS disk check do not work). Downloaded the most recent EasyBCD and made a contribution - but hope to not need to use it again!

PS: didn't really see this kind of problem mentioned in the sticky, at least not where it was apparent to me (just re-read it again to be sure)
And the sticky explains it in point 7 (though admittedly it's not been updated to reflect the 2.1 changes)