We detected this issue yesterday. We are working on a new installer that fixes this issue.
One user fixed it by executing:
sudo find . -name "._*" -print0 | xargs -0 rm -rf
But I would execute the code below in order to backup the files before:
mkdir -p ~/testlink-backup/htdocs/
sudo cp -ra installdir/apps/testlink/htdocs/ ~/testlink-backup/htdocs/
Sorry for the inconveniences.