Hello and welcome to the forum.
First make sure that you are using the latest driver available from the hardware manufacturer for the specific network adapter (presumably wireless) that you are currently having issues with
Second check with your wireless router manufacturer's website and make sure you are using the latest firmware available for your specific device.
Then a couple other things to try might be to
Change the wireless channel you are using change it from whatever it is currently set to, to 3 or 11 see if that makes a difference.
Change your wireless security settings.
Test it temporarily by running it open (no encryption) see if that makes a difference. Then change it to WEP, then to WPA, then to WPA2 if available...