Are you using DosBox 0.65?

use vsync in dosbox and force it to use 60hz... or something like that.

yes, i use 0.65.
franpa, how do i do that?

I'm not sure whose builds are currently using the vsync patch (if the one you're referring to is the one I wrote). To my surprise I noticed it in one of ykhwong's builds recently, but it wasn't functional due to a problem in the integration I guess. Perhaps someone else's build has it working. I don't think 0.65 or CVS have it.

Anyway, the vsync setting can't fix the problem. Rather than change the host's timing, it just changes dosbox's internal (fake) vsync timing -- which you can sync to the host's timing if you like for smoothness.

wiki: I presume you're using Windows. Have you tried running other apps fullscreen? Perhaps you should try running another emulator fullscreen - preferably one that allows you to select the resolution - and see if that has problems as well. My guess is that your drivers are set to attempt an unsupported refresh rate for certain resolutions. If you reinstall your lcd and/or gfx drivers, you may find the problem fix itself if you're lucky.

Edit: For a quick fix (without solving the underlying problem), you can try editing your dosbox.conf so that the fullscreen resolution is equal to your desktop resolution. That might set the same graphics mode as your desktop and allow you to use it fullscreen.

Oh yeah.. I've never had this experience before... but, you should verify that any drivers or associated apps for your old display were uninstalled. If you somehow still have them, then uninstall them.

You probably need to set a higher resolution and/or use a scaler in the dosbox.conf. LCD Displays mostly can't handle native Dos resolutions at 320x200 in fullscreen (how they handle the bios messages I don't know but with dosbox and other apps you might run into that problem).

I had the same problem.

I took the advice here and tried a few things. The only thing that worked for me was changing the aspect attrib in the .conf file to TRUE. I tried first tinkering with the fullresolution option, that only made the app centered on the screen, not bigger. Making the aspect attrib true is the only thing that helped. The only problem I found was that after I'd "Exit to DOS" in whatever app or game I was using, my monitor would then give me the "Freq out of range" error message. At that point, it doesn't matter, though, because I am already done with the app anyway. Just CTRL-ESC out to Windows or ALT-ENTER out of fullscreen mode.

Hope it helps.

Maybe RefreshForce would work here?
http://www.pagehosting.co.uk/rf/

The following Modelines give you a totally VGA compatible video signal, which any monitor should handle:

1Modeline "640x350" 25.174825  640 656 752 800 350 387 389 450 +HSync -VSync
2Modeline "640x400" 25.174825  640 656 752 800 400 412 414 450 -HSync +VSync
3Modeline "640x480" 25.174825  640 656 752 800 480 490 492 525 -HSync -VSync
4Modeline "320x200" 12.587413  320 328 376 400 200 206 207 225 -HSync +VSync Doublescan

Note that modelines are a Linux thing, on Windows the program "PowerStrip" can be used for the same purpose.