I have patch 1.29 on my system but still can't join stacks of similar units together. The only modifiers I have on my game are various graphics upgrades. I did not modify the civ3mod file. Anyone else have this problem or know what I'm doing wrong? Thanks in advance for your input.

Is your army full? An army has a limit of 3 troops unless you have the Pentagon. (then you get 4).

I'm not talking about armies, I'm talking about groups of units of the same type (e.g., workers, Riders, etc.) using a command that lets them be controlled all at the same time for movement purposes.

You don't "join" units together unless you're taking about armies. To move a stack of the SAME ACTIVATED (no fortified) units, select one of the units press J and click on a square.