It could be due to incomplete search paths settings in AutoCAD options settings.
Try this link (for AutoCAD Map) but Civil will be similar:
http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=14986736&linkID=9240857
It lists the minimum required support paths for each release of AutoCAD.
Worked for me.
I realize that this post if very old but since it pulled up while I was searching for a resolution to the same issue described here, I decided to post a link to my solution on this thread in case others find their way here in the future. This solution should also fix visibility problems for other missing palettes as well such as Sheet Set Manager and the Properties Palette.
My solution:
More detailed step by step instructions can be found here: Missing Toolspace in Civil 3D
Tom Richardson
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Tom Richardson
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