I'm using ubuntu 14.04 LTS. When I start my pc and click on any bookmark from the file manager it shows this error:

Unable to find the requested file. Please check the spelling and try again.

Unhandled error message: Error when getting information for file '/media/angel/DOC/edu': No such file or directory

But when I open DOC drive and again clink on the same bookmark it works properly. Can anybody tell me why is this happening and how to solve this issue?

Edit: Output of lsblk is following: (ubuntu is installed in sda5)

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT

sda      8:0    0 119.2G  0 disk 

├─sda1   8:1    0  91.3G  0 part 

├─sda2   8:2    0     1K  0 part 

├─sda5   8:5    0  24.1G  0 part /

└─sda6   8:6    0   3.8G  0 part [SWAP]

sdb      8:16   0 465.8G  0 disk 

├─sdb1   8:17   0  93.2G  0 part 

├─sdb2   8:18   0     1K  0 part 

├─sdb5   8:21   0  93.2G  0 part 

├─sdb6   8:22   0  89.3G  0 part 

├─sdb7   8:23   0  93.2G  0 part 

├─sdb8   8:24   0  93.2G  0 part 

└─sdb9   8:25   0   3.8G  0 part 

sr0     11:0    1  1024M  0 rom  

After opening the disk drive the output of lsblk is bellow:

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT

sda      8:0    0 119.2G  0 disk 

├─sda1   8:1    0  91.3G  0 part 

├─sda2   8:2    0     1K  0 part 

├─sda5   8:5    0  24.1G  0 part /

└─sda6   8:6    0   3.8G  0 part [SWAP]

sdb      8:16   0 465.8G  0 disk 

├─sdb1   8:17   0  93.2G  0 part 

├─sdb2   8:18   0     1K  0 part 

├─sdb5   8:21   0  93.2G  0 part 

├─sdb6   8:22   0  89.3G  0 part /media/angel/DOC

├─sdb7   8:23   0  93.2G  0 part 

├─sdb8   8:24   0  93.2G  0 part 

└─sdb9   8:25   0   3.8G  0 part 

sr0     11:0    1  1024M  0 rom

The output of sudo blkid gives the following information about sdb6:

/dev/sdb6: LABEL="DOC" UUID="04280A22280A12FA" TYPE="ntfs"