I did a dist-upgrade after quite a long time and got about 800MB worth of updates. I had grub from a different distro that used to host a few other distros besides LMDE. Everything went through fine with the updates except when i rebooted my machine the original grub was overwritten, most likely i chose to update grub during upgrade, don't remember it clearly. But now the display during grub is completely messed up, i can't see anything and screen is full of junk characters and subsequently Mint boots up. Initially usb mouse behaved weirdly, quite slow and very erratic but that got fixed with another reboot. However my original grub is still gone and i can't boot into any of the other distros. Tried installing burg but didn't had much success there.
Can anyone please suggest how to fix this issue.
I think you have selected to install grub2 to MBR and had some hiccup there if updates has something to do with grub-pc, grub-common or kernel upgrade.
I normally do not allow any upgrade to mess with my MBR since I have multiboot too many partitions. Any updates with grub or kernel change always do something that might rewrite MBR.
Which version of grub you used on controlling your MBR?
grub legacy? or grub2?
if grub legacy, just boot from the original Live CD, on terminal , get into grub prompt, then do root (hd0,x), setup (hd0),,, this should reinstall the grub legacy into the MBR
if grub2, follow grub2-documentation to reinstall grubhttps://help.ubuntu.com/community/Grub2
if still have problem booting any partition, goto get RIPlinux iso, burn into CD, boot computer, and select an option to boot /dev/xxxx of 32- or 64-bit, amend xxxx to sdxy of your partition, then boot into the partition that you choose to install grub onto MBR, and reinstall grub ( instruct depends on grub legacy or grub2.