I had to copy the yappsrt.py file from util/newconfig to the tyan/s2881/s2881 directory, and then everything worked fine.
Sounds like either you have a broken or a brand new or a really old python version. What python version are you using?
Sounds more to me like the PYTHONPATH is not setup correctly. The reason it works the 2nd time is that python has compiled the module into a .pyc in the current directory and now doesn't have to go look though PYTHONPATH to find the module.
Modules either need to be in the current directory, have the proper path to them specified, be in PYTHONPATH or be placed in the default locations under the python tree.
This kind of stuff happens all the time with python based software.
I don't see any difference between this and having your include or library paths set properly in "C". I don't know of any language that will go searching your entire hard drive looking for files when it can't find them where it expects them.
-- Richard A. Smith