According to a Macworld online article, there is a problem with RAM cards not fitting properly in 3400s. The result is that the RAM card may pop loose. The article stated that a foam strip is needed to fix the problem and that Apple is now installing these in new 3400s and will supply the strip to owners of existing 3400s. However, as now pointed out by another Macworld article (and confirmed on the MRP), tech support at 800-SOS-APPL has no information yet on sending out these foam strips. Eric says it will be a few more weeks before they are available.
b. There is a confirmed incompatibility between OT 1.1.2 and PowerBook 3400s running Mac OS 7.6 (see Apple TIL file). The presumption was that this would be fixed with Mac OS 7.6.1. However, as reported by Eric (who is a 3400 owner) on the MRP, this appears not to be the case. The current recommendation is that 3400 owners should stay with OT 1.1.1.
c. In an issue that probably applies to all PowerBooks updated to 7.6.1 (which reduces the number of low battery warnings from three messages to two), Bryan Goldstein writes: "People are reporting that within just seconds of the first dialog box being dismissed, the second one comes up and the computer shuts off before the user has a chance to take any action (such as save the text or whatever). In addition, the computer often has to be restarted from a cold shut-down; there is not enough power left to keep the CPU in sleep mode."
Update: Several users report not having the low battery fast shut down problem.