tool palette - "unable to execute tool. Class not registered."

[bwarchitect]

When selecting wall tool on palette. dialogue box stating "unable to execute tool. Class not registered." appears and does not allow input of wall style into existing drawing. Same thing happens to all wall, door, and window styles. Existing drawing allow selection of walls, changes to wall style, and copying.
Any idea how to fix problem?

[H-Angus]

When selecting wall tool on palette. dialogue box stating "unable to execute tool. Class not registered." appears and does not allow input of wall style into existing drawing. Same thing happens to all wall, door, and window styles. Existing drawing allow selection of walls, changes to wall style, and copying.
Any idea how to fix problem?

Have a look at the similar threads below.