Yep, this is one of those problems that don't have a good fix. Some have more trouble then others.
The item up the tunnel is the "serpent idol". (You can do a search for that and read all about this)
With it you can get the "book of the serpent".
The book tells you how to answer the questions that you will be asked by the "spirit of Xydusa"
This item in the Best Tips tells what is in the book so you can give the anwers.
http://www.ironworksforum.com/forum/...9&postcount=56
I can usually get into the tunnel but it takes a lot of trys. So just do the rest of the temple and use the tips for the answers when you need them.