Instructions for future bug submission reference -
1. Go to http://beta.heroesofnewerth.com/
2. Type in your account information
3. Select 'New Bugs'
4. Fill in required fields
5. Submit form
Back on topic, try to remove the rootkit folder of Heroes of Newerth. There could be something that needs fixing in there that was not overwritten when you reinstalled the game. Uninstall Heroes of Newerth. Go into your rootkit and remove the Heroes of Newerth folder completely. Then, install Heroes of Newerth. Download the latest patch.
I am no computer expert, but this process has fixed many start-up bugs in previous games I have played. If this does not work, try contacting HoN through the future bug submission reference listed above. They have smart people who can assist you.