Dual Boot: Windows 8 Session Lost After Hibernate/Sleep – Ubuntu 12.04

From a similar question on Super User:

Generally speaking, you can hibernate one operating system and boot the other. Each system's state is saved in its own swap space, so you must not share the swap space between the two operating systems.

There's one thing you must pay attention to: while a partition is mounted in a hibernated operating system, you must not access it from other operating systems. With most filesystems, this is likely to destroy your data. (This doesn't apply to network filesystems mounted from another machine, these are designed to be mounted from multiple places at once.) Exception: if the shared partition is NTFS and it's not the Windows boot partition, it's safe to share at the filesystem level (but you'd better not keep a file open in a hibernated application, so it's better to unmount the shared partition before hibernating anyway).

You need to purge and reinstall GRUB this way:

1. run Boot-Repair --> Advanced options
2. go to the "GRUB options" tab, tick "Purge GRUB then reinstall it"
3. click Apply

Indicate the new URL that will appear if any problem.