marybuntu@marybuntu-NV59C:~$ sudo gparted
[sudo] password for marybuntu: 
======================
libparted : 2.3
======================

(gpartedbin:5359): GLib-CRITICAL **: Source ID 7 was not found when attempting to remove it

(gpartedbin:5359): GLib-CRITICAL **: Source ID 6 was not found when attempting to remove it

(gpartedbin:5359): GLib-CRITICAL **: Source ID 26 was not found when attempting to remove it

(gpartedbin:5359): GLib-CRITICAL **: Source ID 25 was not found when attempting to remove it

(gpartedbin:5359): GLib-CRITICAL **: Source ID 31 was not found when attempting to remove it

(gpartedbin:5359): GLib-CRITICAL **: Source ID 30 was not found when attempting to remove it

(gpartedbin:5359): GLib-CRITICAL **: Source ID 34 was not found when attempting to remove it

(gpartedbin:5359): GLib-CRITICAL **: Source ID 33 was not found when attempting to remove it

(gpartedbin:5359): GLib-CRITICAL **: Source ID 37 was not found when attempting to remove it

(gpartedbin:5359): GLib-CRITICAL **: Source ID 36 was not found when attempting to remove it

(gpartedbin:5359): GLib-CRITICAL **: Source ID 40 was not found when attempting to remove it

(gpartedbin:5359): GLib-CRITICAL **: Source ID 39 was not found when attempting to remove it
/dev/sdb contains GPT signatures, indicating that it has a GPT table.  However, it does not have a valid fake msdos partition table, as it should.  Perhaps it was corrupted -- possibly by a program that doesn't understand GPT partition tables.  Or perhaps you deleted the GPT table, and are now using an msdos partition table.  Is this a GPT partition table?