Warning: This is a procedure that can bork your working copy. Backup and test to make sure you can recover before you even think about doing this.

Regarding this post:
http://andrew.hedges.name/blog/2009/01/25/how-to-recover-from-checksum-mismatch-errors-in-svn

Quickly remove .svn directories from a working copy linux
cd /to/svn/working/copy/dir

e.g.
/etc/squid
find . -type d -name .svn | xargs rm -rf

Checkout a fresh copy of the working copy somewhere else.

cd $HOME

svn co http://yourreposserver/path/to/squid

cd squid
find . -type d -name .svn | xargs -ISVN cp -arv SVN /etc/squid/SVN