difficulty in opening files

[Dr. Md. Aminul Islam Khan]

Hi,

Using ubuntu 9.04, postgres-0.9rc1,
1. installed: OpenSP-1.5.2, openjade-1.3.2, libdbi-0.8.3, libdbi-0.8.3-1
--with-pgsql.
2. installed gnucash-2.3.15
3. Started gnucash, it opens all the four files present under File.
4. Now, File->Open->Open -> dialogue box: open...
Data Format: file, 
Location:/home/aikhan/.gnucash/books/Ahmadlab-> Open-> dialogue box
says: Can't parse the URL file:///home/aikhan/.gnucash/books/Ahmadlab
(for information: The file is present and was last modified 08/29/2010)
What am I doing wrong?

Any guidance is highly appreciated.

aikhan