Test project ,which was created first , had disappeared from the list of projects after creating new test project and assigning roles to tester for this project.
I have 3 test project in DB, but I have only 2 in the list of projects the TestLink page
I'm encountering a similar problem with 1.7.5 and was considering an upgrade to resolve the problem. Basically, I use the Home=>Create New Test Project to create multiple projects. Only the first Test Project is visible anywhere in TestLink. I then used Create New Test Project to recreate projects with the same names. This fails saying the invisible Test Projects exist. However, I can't do anything with them.