Subversion >= 1.5.7 and >= 1.6.4 sometimes reports "Svndiff contains a too-large window". Has been reported as happening during svn checkout/commit/update and svnadmin load/dump/verify at least.
Some reports of the problem:
- http://svn.haxx.se/users/archive-2010-02/0453.shtml (on checkout, verify, dump);
- http://subversion.wandisco.com/forums/2-subversion-community-support/556-svnadmin-svndiff-contains-a-too-large-window.html (on svnadmin load);
- https://gforge.inria.fr/tracker/?func=detail&aid=9625 (on checkout; suggests trying to repair the repo with fsfsverify.py).
The code that introduced this check: