cvsup failing with "ASSERT failed"

[none]

A couple of times, now, on both FBSD-5.1-CURRENT and FBSD-4.8-STABLE whilst 
running with 2MB of RAM, cvsup has "croaked" with the following error:

***
*** runtime error:
***    ASSERT failed
***    file "/usr/ports/lang/ezm3/work/ezm3-1.0/libs/m3core/src/runtime/
common/RTHeapMap.m3", line 35
***
    use option @M3stackdump to get a stack trace
Abort trap (core dumped)