Based on my usage of UnrealIRCd, a G-line is placed on an IP address. Your IP address, from your post, is 126.96.36.199
The network may have a G-line entry that matches 217.75.128.*, so anyone that tries to connect from a matching address will be g-lined. This is usually the case when a person causes problems, gets g-lined, then tries to evade the g-line by using a different IP address.
Regarding the reason, it is given, in the 2nd last line
-irc.UniBG.org- *** Banned floood (2007/8/29 17.57)
Note that the date and time of the g-line is being given. The date and time might not match yours (might be earlier, might be later), as it is based on the time where the server is located, or GMT (I can't tell which it is from what is poated)