The runaway success of the Elecraft KX3 has resulted in a sharp increase in the number of users of KComm. Even those who use a full-featured logging program in the shack find the simplicity of KComm and the compactness of its user interface (which was designed to fit a netbook) better suited to portable operating.
I received an email from a KComm user in Vienna, Wolfgang OE1MWW who wrote that he found the option to "Use PSK modem" (which uses AE4JY's PSK Core DLL to operate PSK31 using the sound card) was disabled on his laptop running Windows XP SP3 though it was enabled on his desktop running Windows 7 64-bit. Wolfgang eventually found that replacing the file PSKCore.dll that was installed by KComm with one dowloaded from AE4JY's website cured the problem.
I am surprised and a bit mystified as to why this occurred. My shack PC also runs Windows XP SP3 (I prefer to stay as far from the bleeding edge as possible) and it uses the same version of PSKCore.dll as is installed with KComm.
KComm's version is much smaller so I'm hazarding a guess (since I can no longer remember) that it may have been compressed using UPX, an executable file compressor. I used to have a bit of a mania for compressing executable files so I could claim how small they were compared to certain other ham radio bloatware, but in these days of 100GB hard drives it's probably rather fatuous. Possibly the compression caused an issue with some security software?
Whatever the reason, I'm grateful to Wolfgang for discovering a solution. I have added a note to KComm's Troubleshooting page and updated the installer package to include AE4JY's copy of the PSKCore.dll so hopefully new users will not encounter this problem.