Need help in solving a cookie problem

I don't know if this has been posted before...
There seems to be a problem with cookies on my site, whenever I try to login, I sometimes become a guest rather than a normal user. That becomes a big problem when I try using features that are reserved for normal users only. When I do that I get thrown back to the portal page as a guest. Clicking on 'Forum' makes me a normal user again!
I think this happens because the computers here go through a proxy server rather than a direct connection. When I check my online list, I get many Guest connections coming from both the proxy server and my own ip address. My normal admin account is logged in all right.
I can't clear cookies directly because of certain privileges with the computer. However, trying to use the MyCookies Manager fails most of the time.
Please help!
P.S. I'm using Integramod 1.40 with phpBB Security 1.03
There seems to be a problem with cookies on my site, whenever I try to login, I sometimes become a guest rather than a normal user. That becomes a big problem when I try using features that are reserved for normal users only. When I do that I get thrown back to the portal page as a guest. Clicking on 'Forum' makes me a normal user again!
I think this happens because the computers here go through a proxy server rather than a direct connection. When I check my online list, I get many Guest connections coming from both the proxy server and my own ip address. My normal admin account is logged in all right.
I can't clear cookies directly because of certain privileges with the computer. However, trying to use the MyCookies Manager fails most of the time.
Please help!
P.S. I'm using Integramod 1.40 with phpBB Security 1.03