Blank/white Admin screen with admin.php but OK with wp-login.php

Hello, about a week ago I installed Wamp and WP 3.1 without problems. It all still at default values, apart from using the IP address of the host in WordPress and Site address. The first time I logged into Admin was OK but every time after that I got a blank/white screen. I tried the suggestions in the forum but found that running install.php and using wp-login.php worked. I could then use admin.php to login on the host PC but other PCs on the internal home network would get a white screen unless I used wp-login.php. I’ve reloaded the admin files. I could just use wp-login.php from now on but thought there may be an issue that will cause problems in the future. Should I just leave it as it is? Any suggestions that may resolve this? Thanks, David