Problem:

A 'svn up' command, or other svn commands result in the following error message:

• svn: Valid UTF-8 data
  (hex: 72 72 72 20 61 72 72 72 72 62 65 69 74 65 6e 21 20 2d 20 53 6b 79 70 65)
  followed by invalid UTF-8 sequence
  (hex: 99 20 43 68)

Explanation:

There is a file with non-UTF-8 characters somewhere

Solution:

Try 'svn info' in your projects subdirectories. When there is no error msg, the current dir plus subdirs is ok. If there is the error msg, go through the subdirs until you find the invalid file