Unknown Error ?

[Albertas]

Hello,

I have made an application that hosts a Web Service using WCF. At
first sight when I start the service, connect to it with client
application everything works fine. The problem comes after 10 -
15minutes, when the host application terminates and I get windows error
display message. However the application process is still running. I
can't even shut down it using task manager. When I try to run project
again I get error:

HTTP could not register URL http://+:8000/VirtualLab/. Another
application has already registered this URL with HTTP.SYS.

I use IIS 5.0, ws binding is: basicHttpBinding.

Here is the error log:
#Version: 1.0
#Date: 2006-12-19 18:48:55
#Fields: date time c-ip c-port s-ip s-port cs-version cs-method cs-uri
sc-status s-siteid s-reason s-queuename
2006-12-19 18:48:55 127.0.0.1 1115 127.0.0.1 8000 HTTP/1.1 POST
/VirtualLab/Methods 503 - Disabled
2006-12-19 18:48:55 127.0.0.1 1165 127.0.0.1 8000 HTTP/1.1 POST
/VirtualLab/Methods 503 - Disabled
2006-12-19 20:07:21 127.0.0.1 1471 127.0.0.1 8000 HTTP/1.1 POST
/VirtualLab/Methods 503 - Disabled
2006-12-19 20:07:21 127.0.0.1 1678 127.0.0.1 8000 HTTP/1.1 POST
/VirtualLab/Methods 503 - Disabled

Can anyone advice me how to resolve this problem ?

Could it be a result because of frequent calls to Web Service ?

Thank You