I went to commit my iPhone app code using RapidSVN, and as I performed a routine commit to the SVN server (I use beanstalk), I got this error message: “Error while performing action: commit failed (details follow): Checksum mismatch for …” Very annoying.

Temporary Fix
The temporary fix is to check out another copy of your project from the SVN server and copy/replace the file with the checksum mismatch. Then recommit and you should have no issue.
Permanent Fix (at least for Xcode projects)
You can set your subversion config file to ignore certain file types on commits. To do this, find your subversion/config file and set this property:
global-ignores = (and set whatever file types you want)
You can use wildcards like * as well. So in my case, for the example shown above in the screenshot, I added *.perspective* to my global-ignores property. Should fix that issue!
To quickly find the config file on a mac, open the terminal and type:
cd ~/.subversion/
open config
On a PC, I believe it’s located here (but I have not verified):
C:\Documents and Settings\<user>\Application Data\Subversion
I hope all this helps!