Hmm, did ya try the following?
First, if ya using find the DOSBox-0.74 version, look for the DOSBox-0.74 Options ( I am using XP, so the path for me is usually menu --> All Program --> DOSBox-0.74 --> Option --> DOSBox-0.74 Options)
Open the DOSBox-0.74 Options.
Find the [cpu] section of the DOSBox-0.74 Options.
If ya find a line
cycles=auto
change it to
cycles=max
Save and see if it work.