My documents' icons started getting this blue two arrows symbol on them. What could it be? It started appearing after I messed up with Norton's backup settings, could it be related to that?

Your Norton software is indeed responsible for this. Norton 360 adds three indicators to the file icons to flag their backup status:
• A check in a green box to show the file’s backup is current;
• A chevron (») character in a blue box to show that the file has been changed since its last backup; and
• A slash in a grey box to show the file has been excluded from the backup set.

You can turn off the backup indicators by clicking Settings in the Norton 360 main window, by unchecking the Backup Status Indicators checkbox.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]

Thanks! That worked.