What could be nature of this problem (session probably)?

[Chris]

There are 2 games. Both on the same machine, the same IP, the same domain (just subfolder), the code is almost identical (a bit different version of the same game, beta world to be precise).

A player can login to one and can not to the other. He is getting an error as if the session was not present (userid that is storted after login is not existing). The player changed the ISP and then it happened, before there were no problems.

The error with the code is almost impossible since it was checked with 8 different games and 4 can be accessed and 4 not by the player.

How could this be possible? What could be the reason?

[dsheroh]

The player changed ISP, but the game is still running on the same server as before?  Are any other players (in particular, other players using his new ISP) also having similar problems?  Is there any chance that the player may have switched browsers or other software when this problem started?

[Chris]

The game is still running on the same server. No change of the code as well.
As for other players, I don't know, players report many things... Sometimes they report similar thing (but usually it is some nobish mistake on their side, they misread something, etc). Hard to tell.
No, it was tested using various browsers.

I just wonder how such thing could be possible theorethically. How another (very similar script) in another folder could behave differently for one user? It could not be even blocked by firewall so selectivelly, or anything... Any network problem would also affect both scripts...