Gosh,
 
I thought about this one for just a little bit.  I cannot reproduce it so I
suspect that it may have to do with your database.  You may wish to verify
the access modes for your datasets and dataitems.  There may be something
funky in the way a class can read/write using mode 1 but not be allowed to do
much with read only, mode 5.
 
Kind regards,
 
Denys. . .
 
 
P.S. Let us know!