need monitor help pls

I have reeally shitty and old CRT 15´monitor but it worked for me perfectly fine for about a year, but now it starting to piss me off. when i start ET it goes black screen with a note : "Attenton out of range H: 107.8kHz V:99.75Hz" i figured out it has smth to do fith fps, coz when i want to change frequency in windows to 100 or higher it goes the same, but i didnt change any fps settings in ET and it started doing this, even if i lower my ingame fps to 76 it still show the same attention sign. Pls help, thx