Help ! Btrieve for Xenix 386

[S. T. Tan]

I am using the Btrieve ver 4.11a for Xenix 386.
I encountered a strange thing happened in Btrieve.
First, I open a number of Btrieve files (12 files). 
After manipulating (delete, insert, retrieve, update) the contents of
each file for a while, suddenly the routine from Btrieve (btrv) return an
error number for "File not opened".
I am sure that I have not closed any file.
Does anybody has a similar problem ?
Is Btrieve for Xenix reliable ?
Is the patch file for Btrieve for Xenix available ?

Your help will be appreciated.
swie at umn-cs.cs.umn.edu