#11 "this" spontaneously changes address over method calls

[Anonymous]

In a large project (qmake):
class QTextStreamPrivate has two private functions,
scan() and fillReadBuffer().

suddenly during execution, the "this" pointer
spontaneously changes address between
a call to scan() and scan() calling fillReadBuffer()
resulting in a Segment fault.

I've tried substituting this->fillReadBuffer(),
but gdb tells me that "this" has changed
when making the call.

I'm having trouble recreating the problem in
a simpler setting than the full qmake project.
It seems to happen when another object
(of class QMakeProject) recursively creates
entities of itself...

gcc --version says 4.2.4 (adtools build 10090118)