I've search the causes of session data loss, and have tried a lot of the methods to fix it, to no avail.
What happens if a webpage opens a new window and requests a php page in that window, which
does a session_start() of it's own. Does it get a different session ID than the primary window?
It seems to work, then at times it doesn't work.
This page does not change any of the session values, just reads them.
Basically, the new window pulls a file from the server, then pushes it to the client giving it a new filename
(the file is stored under a unique name on the server, and it's name supplied by the client is stored in a database - so when the file gets pushed to client - they only see the name they gave it, not the actual filename it's stored under on the server).