Description
Due to a problem in the ModelSim-Altera software version 6.6c, you may be unable to highlight a section of waveform for wave editing even though edit mode has been enabled.
Resolution
To work around this problem, copy the file wave.tc_ to the directory <ModelSim-Altera installation directory>/tcl/vsim
and replace the existing file.
This issue is scheduled to be fixed in a future release of the ModelSim-Altera software.