Often, another mod causes this type of conflict.
Have any that monitor chat? I'm talking _any_ thing that might watch chat.
Emoticons, custom chat hud, punctuation, etc.
Do you get any errors in server console when you attempt to use ULX ! chat commands.
We've written ULX to be as 'nice' and compatible as possible regarding other chat monitoring scripts, but we can't guarantee the same for others. :/