I resupped the kernel last night, and sure enough, this seems to have 
solved my pppd lockup, but now all my xterms are dying at startup with the 
error:

xterm: Error 23, errno 25, inappropriate ioctl for device

I notice that a lot of new code has been committed for compat_43 support?  
Could this be related (my xterm binaries are quite old, around 1.3 alpha 
vintage)?  Is compat_43 on by default, or does it need to be added to the 
config files as needed?