CHECK.PHP GOTCHA (upto ver. 1.3.9-1)
Using check.php before the first installation will lead to errors, because once the script is done checking permissions, it will start checking SQL and next error will stating that gl_sessions table is missing.
Here is how to deal with it.
Run for the first time (or several times) while getting permission errors. Make changes (for example, chmod from 775 to 777) until the kind of error you get from check.php will change.
That will indicate that permissions on error.log are done correctly and now script moved to SQL check-up (about what you can now learn, by reading your error.log)
for you being at stage of pre-installation that will be enough. Stop running this script and proceed to the next step, step 4
NOTE: check.php only checks first folder (logs) for permissions before SQL error, so images/ and inside articles/ and userphotos/ were not checked. You can easily guess, that the kind of permissions worked on log folder will work on those, so just do the same chmod on them