If DragThing suddenly stops working, or gives error messages, ask yourself if you recently changed anything. Did you upgrade to a new version of the Mac OS, or install a new piece of software? If so, there might be a connection.
One good test on Mac OS 9 and earlier is to use the "Extensions Manager" control panel to switch off any third-party extensions and control panels. The "base" set of extensions is a quick way to do this, as it corresponds to the setup your Macintosh had when you originally got it. If you don't see any problems with DragThing with a minimal set of extensions, it's very likely that something else you have installed since then is causing the problems. If you turn things back on, a little at a time, you can work out what's to blame.
It might be that there is a later version of the software available, or that it just doesn't work well under the version of the operating system you have.
Mac OS X doesn't have the same underlying architecture as Mac OS 9, so extension problems aren't likely, but it may be that other recently installed software is at fault.
Another possible cause of problems is damage to your "DragThing Preferences" file. All your docks and settings information are stored in this file by default, and if it becomes damaged this can make DragThing behave in an unpredictable manner. If you have a backup, it might be worth trying it, otherwise you may need to remove the file and recreate your docks again.
And of course DragThing might just have a bug. Check on www.dragthing.com to see if it is a known problem, and if I have a newer release of DragThing available that fixes it.
But if you think you've found a problem I don't know about, please tell me. It's helpful if you tell me what version of the Mac OS you are running, as well as the text of any error messages you are seeing. If you see a crash, any log files are appreciated too.