A little light on the horizon.
<font color=BROWN>ToCheck</font> * Setting Windows Explorer to show hidden files & folders
<font color=BROWN>ToCheck</font> * Verifying Application Cache for CS2 Within Steam
<font color=GREEN>N/A</font> * Disabling Steam In-Game Community
<font color=GREEN>N/A</font> * Uninstalling Steinberg CuBase and associated drivers
<font color=GREEN>N/A</font> (Scirra FTW! ;-))* Uninstalling GameMaker Steam version (in case of sabotage)
<font color=GREEN>N/A</font> * Uninstalling All Non-Valve Games from Steam
<font color=GREEN>N/A</font> * Uninstalling Skype Click-to-Call
<font color=GREEN>N/A</font> * Uninstalling EA Download Manager & all games that need it (Spore etc)
<font color=BROWN>ToCheck</font> * Disabling Every Plugin, AddOn and Theme within FF & IE (left Chrome alone)
<font color=BROWN>ToCheck</font> * Using Driver Sweeper to remove any outdated graphics drivers (Nividia)
I'll check the things I can do on my system, and try it after every step. If it still occurs I'll have a look at ohter third party software that may interfere with C2/Steam