using patch to manage differences

Please help. Bit of a newbie question.

I have the same application in three separate environments, Lets call then
A, B, and C. Each is identical except that each has configuration files
that store environment specific settings (database connection strings,
folder locations, etc.)

I imported placed all the files under version control for installation A. I
then carefully edited just the configuration files to have the settings for
Installation B and used Tortoise SVN to create a patch file, which I placed
under source control. I reverted all the changes and verified that the
settings were correctly "rolled back" for installation A. I then applied
the patch and verified that the application was correctly configured for
installation B. Feeling confident, I reverted again and repeated the above
for installation C.

At the end of this process, I had all of my application files for
installation A plus two patch files for installations B and C under my
Trunk.

I then made some updates to installation A and commited these changes.
Knowing that these changes need to be made to installations B and C, I
attempted to apply the patch I saved for Installation B in order to merge
those changes in order to create a new patch for B. When I try to apply the
patch however I receive an error, saying the patch file seems to be
outdated. It then displays two lines (one from Installation A and one from
the Patch file) and states that they do not match. In fact, they do match
except that there is a tab at the beginning of one line and 4 spaces at the
beginning of the other line.

I have tortoiseMerge set to ignore all whitespaces. Why can I not apply
this patch?

Please tell me this is a bug and not a feature. I am using TSVN 1.5.5 build
14361 32-bit.

Is there a workaround or an option that I can specify to override this
behavior (or force the merge)? I don't mind if there are conflicts for me
to resolve. I just need the merge to to apply the patch.

-- 
Kerry Carroll
carrolky_at_alumni.uc.edu