How to [mount_point cannot contain the following How to [mount_point cannot contain the following chacharacters: newline, G_DIR_SEPARATOR (usually /)]

Open gconf-editor in terminal:

$ gconf-editor
In the left panel:
Goto:

System -> Storage -> volumes

Here you will see the mount point you specified for the device.
Change it to just a single word (OR just remove it :) )
Thats it. Replug your device.

Enjoy!!!

EDIT:
1. Do not use sudo for this purpose.
See this comment by Anonym... (Thanx to Anonym) for detail.

2. Sometimes instead of System -> Storage -> volumes you may also get System -> Storage -> drives , depending upon what you messed up. The rest process is same.