Verify you have adequate harddrive space and RAM on your system. You may need to update your video driver. To test this change your video settings to the Windows standard VGA display. Run Netscape to see if the problem remains. If not contact your computer provider for updates to your video driver software.
Conflicts can occur with programs loaded by windows during startup.
Try closing all programs and retry. Occasionally, something you have loaded in your config.sys or autoexec.bat may interfere with Netscape. Try to temporarily remove some drivers loaded in these files and retry. If you have this problem try disabling or enabling True Type fonts in Windows 3.x. If Adobe Type Manager running, close it, reboot and retry.