Here is a solution to use your A835 mobile phone with iSync. Use vi or emacs and modify your USBDevice.plist:
% cd /System/Library/SyncServices/MotorolaConduit.bundle
% cd Contents/Resources
% sudo emacs USBDevice.plist
and add, before the last tag set, the following entry:
<key>A835</key>
<dict>
<key>idProduct</key>
<integer>12290</integer>
<key>idVendor</key>
<integer>8888</integer>
</dict>
Now reboot and plug in your A835 with the USB Cable. iSync will find your mobile and you can sync it without problems.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2004031410151793