MacTools Trashback, a utility included with MacTools Pro 4.0, has been reported to affect calculations in FileMaker Pro and ClarisWorks. For example, the formula =0 returns a zero. The formula =ROUND(0,2) should also give a result of zero. With MacTools Trashback installed, this calculation produces .010000000000001.
MacTools Development is aware of the issue and has reportedly fixed it in the latest version.