Macbook external display ISSUES!

Hi,
I got a dell spf220 or something close to that. Its a 22inch widescreen dell monitor. Well I had it hooked up to my macbook through the hdmi to dvi cable. Everything worked great for a while. Then recently I plugged my macbook into a 46 inch hd tv and used that as a monitor. Well, when i tried going back to the smaller monitor, the only way the external monitor would work and link up was through a lower resolution (1024 x 678) or something close to that. (I am at work, sorry!) So anyway, the cord works fine when i plug my girlfriends macbook into my 22 inch display so I am assuming something is wrong with my macbook. My lcd works fine on the macbook- and it even will work with the external on a lower resloultion- however, when i connect them up and try to run 1280 x 800 or whatever the reg is, the external just goes into sleep mood or stays black. It will occasionally flash on.

If anyone has experienced this, or has feedback on what i should do, I would appreciate it!
Thanks

Have you tried hooking to the DVI input on the Dell? (Mini DVI from your MacBook to DVI input on the Dell.) BTW, the Dell native resolution should be 1680 x 1050 at 60 hz.

Regards.