Always get "The connection was reset"

I’m a newbie to wordpress, but I have a very weird problem from the beginning: when I save draft or preview or edit a theme, I always get an error: the connection was reset.
I’ve tried every way I can think, but the problem remains. Here is what I’ve done:
1. I tried both Firefox 4 and IE 8, no good;
2. I used another PC with the same wireless connection, it worked perfectly! Also worked on other PC/Mac, so I’m sure it’s not a problem with the web host;
3. I reinstalled WordPress once, and tried both Chinese and English versions;
4. I tried the VPN provided by my school, and failed, so it’s not my ISP’s fault either;
5. I shut down the antivirus, which is avast!, and some services I thought suspicious, still got the error.
So I’m desperate now! I asked my friend working at the web service department at our school, he had no idea either. I think it is some problem with my computer, but I can visit any other website properly, and I get no problem visiting my website. The error only occurs with wp-admin. I’m currently using Windows 7 32-bit. My host is 000webhost.com, and my site is mr-teen.com (actually nothing there due to this problem :< ). I listed all the softwares related to Internet that I installed below:
XAMPP, avast! antivirus, Cisco VPN Client, FireZilla FTP Client, FF4, IE8, Garena, Skype.
If someone has any advice, I would be really grateful!