I recently observed this issue when a presenter in a Lab class could not select a work plane accurately.  He would hover over the correct plane, but when ‘clicking’ the mouse, a different plane would be selected.  Revit 2012 was being used on a laptop, with an external projector plugged in for the presentation.

I have a feeling that this issue is similar to one I have posted about previously, at this link.  Over at Do U Revit, a comprehensive set of comments may prove useful if you are trying to solve this problem.

Some potential fixes (from the abovementioned comments) may be to:

  • swap monitors from left to right in the Windows display properties
  • make the monitor that is running Revit the primary monitor

Of course, if all else fails:

  • run Revit in a single-display configuration if possible to avoid the issue

I have a few other ideas that I have not really tried for 2012, including:

  • make a new Windows user AFTER connecting the extra monitor or projector, then log in as this user and attempt to use Revit.
  • fully reset the UI and Revit registry data AFTER connecting the extra monitor, and then run Revit (risky).

The other important lesson is this – if you are going to be doing a presentation or tutoring session, TEST your proposed configuration prior to the session.  Five minutes of testing can save a lot of embarrassment!

EDIT May 2012

I recently had this issue after reinstalling graphics drivers and using Revit 2013.  I followed the tip on this Autodesk page to run Revit on the primary Windows monitor – this fixed the problem for me.  You can then drag the Windows 7 toolbar to the secondary monitor if you want max screen real estate on your Primary…

EDIT 3/2011
This issue is still annoying some users.  There is a very comprehensive set of comments over at:

http://do-u-revit.blogspot.com/2009/10/whos-dragging-my-stuff.html

A few different solutions are mentioned at that page.

One of our users experienced a very unusual error today. It seemed to appear randomly (no known cause). But it had happened to him before…

Basically, when any object was selected in Revit, Revit would interpret this as a ‘drag’ command, and the object would be moved upward by a certain amount (about 5% of the screen).
We ruled out Direct3D and mouse problems.

However, when logging in as a different user, the problem wasn’t there! So, we reasoned, it must be a user specific setting.

I deleted the UIState.dat file, as Autodesk Support had told me to try this for a different problem. How do you do it? See below quote from Autodesk Support:
To fix the issue, the UI state can be reset to default settings by removing the UIState.dat file by browsing to the appropriate product folder located in one of the following locations:
· For Windows® XP: %USERPROFILE%Local SettingsApplication DataAutodeskRevit
· For Windows Vista®: %LOCALAPPDATA%AutodeskRevit

However, this DID NOT fix up the click-drag problem.

I then went to the registry:
HKEY_CURRENT_USERSoftwareAutodesk
and exported all of the Revit subtree (for backup purposes).

Following this, I deleted [HKEY_CURRENT_USERSoftwareAutodeskRevit] and all the sub-components.

Amazingly, THIS FIXED the issue!!

I am obviously quite happy with this result. Please use this fix at your own risk.