[Xash]

1. do different servers have different port numbers? If this is the case it could be a firewall issue
2. Try starting a new profile on your computer and try connecting to red with that profile, turn off anything unnecessary, then you can figure out if something installed causes the issue. If it works on the new profile something running in the background is the issue.
3. Have someone with a laptop or another computer try to connect. If it works it's something specific to your computer, if it doesn't it might be a router/modem issue?

Just some thoughts. Definitely odd you can connect to one server but not another.