All http traffic are blocked

[Xperia TX]

I have installed ABP on my mobile. It works fine under wifi connection.

However, when I am connected to the internet via the mobile (2G/3G) network, ABP seems to block all http traffic. For example, I will get the following message when I use the stock browser to goto adblockplus.org
QUOTE
Got the error: Server Error
while trying to obtain http://adblockplus.org
Connection refused
UNQUOTE

Only http traffice is affected: I can visit https sites with ABP turned on under 2G/3G network.

Does ABP use any special ports that may be blocked by my mobile network ISP?

The following are information of my mobile:
Model: Sony Xperia TX (LT29i)
Android version: 4.1.2 (stock ROM rooted)
Browser: stock browser

[Xperia TX]

Forgotten to mention: my ABP version is 1.1.2 build#253