When using the PlanAhead text editor in the PlanAhead tool with "Use tab character" selected, if you open a .v/vhd file using tabs, the columns may be displayed incorrectly.
For example, when I put my cursor on a location in my .v file, it displays a different column number in the lower right when compared to the same location one row down (depending on the number of tabs in each row).
This problem is not seen in a .v file that does not use tabs.
To work around this issue, uncheck the "Use Tab Mode" when using the PlanAhead Text Editor from the Tools > Options > PlanAhead Text Editor.
This issue has been resolved in Vivado Design Suite 2013.3.