Unable to access webmail at one location, but works everywhere else

I've been trying to resolve an issue for the past week and would appreciate it if someone could me out here.

Last week I was trying to set up the mail on my macbook so that the webmail could be accessed through it. I must have entered a wrong port or something because it didn't work, so I simply deleted the account. At about the same time one of my coworkers approached me and said that her email wasn't working. Well, that was just the beginning.

At our office nobody has been able to access webmail on any computer since (internet works, and access to any other type of email account works as well). When we go elsewhere and use other wireless connections there are no issues with accessing webmail.

At the office, we can see the webmail user panel, however, after one types in a username and password they clear as though they weren't entered after pushing enter.

I've checked the router (netgear router) and with our internet provider - there doesn't appear to be any issues.

What could have caused this to suddenly occur, and how do I fix it?

 

Thanks for trying to assist me with this. After several hours on the phone with isupport, my internet provider, netgear and a few emails to cpanel that were not responded to, I was fortunately able to resolve the problem on my own. I simply replaced the netgear router and I haven't had any problems since.