Wamp perfect on localhost, sometimes not when accessed from internet (no replies)

hello
strange problem. I'm writing you after having tried uniform , xaamp and now wamp.
I have googled a lot before posting but I have a problem that's driving me crazy.

Wamp is working perfectly on localhost and - usually - when accessed from internet too.
I click and each page is loaded immediately.

suddenly, without any reason, when accessing the site from outside my LAN, so from internet,
the site stops responding. It gives a blank page, then it restarts normally.

this is quite frustrating. any idea to help me solving this issue?

thanks