computer frezes when downloading in firefox

[stanb5]

Used Avast antivirus briefly and uninstalled it after having conflicts when using Firefox and now using Avira. Before using Avast I had no problems with Sandboxie for a long time.Uninstalled and re- installed sandboxie but the problems still continues. Everything is fine until I download or play a game online and the computer will freeze and have to shut down and re-start. When using Firefox without sandboxie everything is fine.