Try downloading the latest version of GWMC
If that doesn't work, troubleshoot the issue by taking everything step-by-step.
Does the game freeze without mods on a fresh install of the software? If it does not, then there's either an issue with the mods, the installation of the mods or the software media itself.
If it does, then un-install the game, delete any previous game directories and use something like CCLeaner to dust off all the registry keys that are left behind and no longer in use.
Re-install the game after the clean-up process and without any mods, see if the game runs. Take it from there.
I am not sure if the mods are all Steam compatible. Some games are not, so keep this in mind. I'm completely new to GTA IV modding, so not sure what the exceptions are here.Be sure to use something like an ASI Loader when applicable.