Git Cygwin - unable to create any repository - help!

["Paul Umbers" <paul.umbers@gmail.com>]

Trying to create a repository under the cygwin install of git, windows
XP Pro. I can create the initial repository OK using "git init" and
add files using "git add .", but when I come to commit I get the
messages:

error: invalid object d9b06fceac52f6c24357e6a7f85c601
088381152
fatal: git-write-tree: error building trees

git-fsck gives me:

notice: HEAD points to an unborn branch (master)
notice: No default references
missing blob d9b06fceac52f6c24357e6a7f85c601088381152

This is with a simple repository of one directory containing one plain
ascii text file with some text in it. I get similar messages, with one
missing blob for each file or directory in the project, on more
complex projects. At home, I use git under Ubuntu linux and haven't
had any such problems.

The git/cygwin install followed the instruction for a cygwin binary
installation from the wiki and no problems were reported. I've been
unable to find online comments relating to this problem and am stuck.

Any suggestions?

Paul