I have a client using Time Machine with an external Drobo on a Mac Mini running OSX 10.6.8. Time Machine regularly gets stuck during one of its hourly backups. I can follow the steps outlined in this post to stop Time Machine and delete the .inprogress file and Latest folder, then restart Time Machine again:
The problem first occurred in March and the fix lasted for weeks. But the problem has been returning more quickly and now Time Machine usually hangs again after only a day or 2.
Thanks in advance for your help.