I think if you click the mouse again or press Esc or some other key on the keyboard it might unfreeze.

Tried those things to no avail. It just doesn't respond to anything, neither keyboard buttons or mouse buttons.

do you use the same sdl.dll with both versions ?
Some SDL.dll versions generate extra mouse button press events, which lemmings doesn't like.
Not sure if this is the case for your problem though

Nope. Neither with DOSBox 0.74-2 or DOSBox SVN. The thing is, I originally discovered this problem in DOSBox ECE. And I said to myself, "maybe the patches are causing problems". And the rest is history.

Update: I recently discovered that when I press the right mouse button with the title screen locked up, it unfreezes for some reason. And then I can continue to the next level like normal. That's neat, but a little strange...

but which sdl.dll are you using with the SVN ?

With DOSBox SVN and ECE I am using version 1.2.15.0. i don't know what else you want me to specify tho.

and how does it behave if you use the sdl.dll from 0.74-2 with it ?

I just downloaded the game (for testing purposes only!) but couldn't confirm your problem, even with the SDL.dll coming with ECE. Would you please post your .conf file, maybe it has another reason? Do you run DOSBox under Windows or Linux?

Btw.: What makes you think the game has frozen? Because you can't see a mouse arrow? Are the Lemmings at the bottom moving? Can you choose the options with the F-keys?

Qbix, I will test that once I get home.
Yesterplay, I am on Windows and I don't think the conf file is the problem. I'll post a screenshot when I get home.

Qbix, if I use the SDL from DOSBox 0.74-2 on SVN, it lets me continue. Like, it doesn't go to the title screen to then "freeze" but it goes to the summary screen of the next level.
Yesterplay, it looks more or less like this:

The Lemmings at the bottom of the screen don't move, there normally isn't an arrow on the screen, so I can't see it, and I can't trigger things with the function keys. So yeah, it is frozen.