"malformed Scala signature of ByteCode ..."

Are others getting build failures like this:

quick.scalap:
[scalacfork] Compiling 5 files to /scala/trunk/build/quick/classes/scalap
[scalacfork] Exception in thread "main" java.lang.RuntimeException: malformed Scala signature of ByteCode at 4179; reference value other of method orElse refers to nonexisting symbol.
[scalacfork] at scala.tools.nsc.symtab.classfile.UnPickler$UnPickle.errorBadSignature(UnPickler.scala:797)
[scalacfork] at scala.tools.nsc.symtab.classfile.UnPickler$UnPickle.scala$tools$nsc$symtab$classfile$UnPickler$UnPickle$$readSymbol(UnPickler.scala:187)
[...]

with an annoyingly high frequency? I end up having to blow away
build/quick/classes/scalap whenver I do anything the least bit
disruptive (like say going backward a couple svn revisions and
rebuilding without enduring the full 11 minute rebuild.)

I believe the much increased frequency of this specific scalap failure
arrived with r18149:

Author: ilyas
Date: Mon Jun 29 16:09:59 2009 +0000

scalap changed to treat named parameters and package objects

If anyone knows a strategy for dealing with this it'd be great. I have
gotten perhaps overly used to it ("overly" because maybe if it were
worse I'd be forced to work on the build system) but it makes me a
little ill to think of how much time I spend each day on build-related
busywork.