Today i was working with a firm who had Revit 2009, 2010 and 2011 installed on all their machines. Apparently the latest service pack for Revit 2010 has screwed up the thumbnail for all families. Having looked around the web there are thousands of solutions for this issue back when people were upgrading from 2009 to 2010 but none relating to 2010/2011. Until now!
A big thanks to Revit Clinic for demonstrating how to unregister the 2010 revit.filepreview.dll
This didnt do the trick but it did allow me to experiment with this file. Instead of unregistering it, I actually had to re-register it. After that, the thumbnails in 2009, 2010, 2011 worked fine. Here is the process:
Go to Windows Start Menu and...
[Vista Win7: in the text field type cmd]
[XP: click Run... and type cmd].
The command prompt dialogue is launched.
Register the dll by copying this code below and use right click > paste to add the line of code
Note: This example is for Revit Architecture. Change the file path accordingly if you are using a different version or if it is installed in a different location.
regsvr32 "C:\Program Files\Autodesk Revit Architecture 2010\Program\Revit.FilePreview.dll"
If successful you will see a dialogue box advising that the dll has been registered.
You may have to reboot your machine to see the changes take place (but it worked straight away for me).