no the mods are dont have a trouble together... because every mod has his own folders
you play with a sound/speechpack or skinpack ? delete these or install coh a second time and install ef on a clean coh... another reason is your graphic setting, its better all have the same settings... in the past are the most connecting problems on mods because different graphic options on the players who want to join... but not all graphic settings, only the shader quality and model quality... look that all who want to join have the same, either shader quality and model quality high or low...
for example look at a screen from mystic-car
sorry is from german game but u will see which i mean