updating ubuntu 12.04 LTS causes showing low opacity vertical line over monitor

updating ubuntu 12.04 LTS causes showing low opacity vertical line over monitor

i have DELL Latitude e6410 laptop and attach "samsung syncMaster S20R315B" monitor with cable to it. today after updating my ubuntu 12.04, i tried to restart for completion of update process, but after restart i saw vertical line (1 pixle width) over my samsung monitor. i opened the laptop lid and saw laptop monitor didn't show that line. after that, i restarted ubuntu again and start my windows 7 ultimate and saw anything is fine (in both: samsung monitor and laptop lcd). again restart and start ubuntu and saw that line again.
i changed my display cable and saw that line appear when i use ubuntu!
when i tried to capture screen to show you what happened, i didn't see that line in captured picture! :

and i edited this picture to show you what i see in my samsung monitor:

i think this is my graphic card specification (lshw command in terminal) :
 *-display
            description: VGA compatible controller
            product: GT218 [NVS 3100M]
            vendor: NVIDIA Corporation
            physical id: 0
            bus info: pci@0000:01:00.0
            version: a2
            width: 64 bits
            clock: 33MHz
            capabilities: vga_controller bus_master cap_list rom
            configuration: driver=nvidia latency=0
            resources: irq:16 memory:e2000000-e2ffffff memory:d0000000-dfffffff memory:e0000000-e1ffffff ioport:7000(size=128) memory:e3000000-e307ffff
any help appreciated.