Looks like maybe related to
http://forum.cockos.com/showthread.php?t=180277 as I have the LCF file I'm recording to opened in REAPER the same time (as item in arrangement)!?
Couldn't repropduce the crash without REAPER (with the LCF) opened.
FIXED (1.28)
With GIF files there are no crashes at all (even if the file I'm recording to is opened in REAPER).