I gotta say that I am so badly disappointed with both Authorize.net help desk and gateway in general. All I can say: it sux, it can't be compared to PayPal's ease of use and 2CO's simplicity. I'm pulling my hair off for the past couple of days regarding that timeout issue, I've searched each and every corner of an internet by trying to find a decent explanation but all I have is big ZERO. Support staff is obviously striking for some reason, my client is sqeezing me like a lemon, etc, etc. And the award goes to Authorize.net.
I just can't believe someone from the crew is unable to provide a decent and stabile solution to developers.
The only thing I can say is I'll give up this misterious functionality gateway called Authorize.net no matter the money I'm about to lose. One day, when it gets matured, I'll be back. But an experience I had shall never be forgotten.