Skip Press writes of a weird symptom: the lower case "a" disappeared from text in all applications except Key Caps, while running Mac OS 8. He eventually traced this problem to Telephone Manager v.3.1.3. He adds: "I've found other bugs in this software. For example, you can't paste a phone number or text into the cover sheet screens when faxing. You have to type it all in manually, unlike what I had with 7.6.1. An Apple support person on the phone told me he had the same problem when he tried it."
Update: Andrew Robinson writes: "I have noticed a similar occurance with my PowerMac 6500/300 with Apple Telecom 3.2.2 installed and OS 8. After configuring some of the settings for Apple Phone, the 'a' key was disabled. I went back over my settings and noticed that the preference to 'answer' the Apple Phone from any other application when receiving a call was set to the 'a' key from Command Space bar. After resetting this, my 'a' key returned with no further problems."