My contact at MicroMat provided an explanation for this: TechTool Pro apparently includes a database of pirated serial numbers and serial numbers from returned copies of the program. With each new update to TechTool Pro, this database is updated as well. When you launch TTP, if it detects one of these serial numbers, it self-destructs, deleting some of its own resources so that it can no longer run. Nothing else on the hard drive should be affected. "While this doesn't cure our piracy problem (which is pretty bad), at least pirates (once discovered) are forced to use older versions or do without."
TechTool (the freeware version) does not have anything like this, so you should not get the -192 error problem with TechTool. However, the error did happen to me when using TechTool 1.1.4. I was attempting to rebuild the desktop of my 3400 at the time. MicroMat had no explanation for this.