Growing VSZ with timers in LWM

I am running CL-HTTP on LispWorks and observed the following behaviour in
LispWorks for Macintosh:
Whenever I reset the timer with
reset-timer-absolute
the virtual size of the application is growing (about 1 MB) and cannot be
reduced with garbage collection.
You can see it with 
ps ux
in the field
VSZ
The application crashes when VSZ exceeds 3 GB.
The same application runs without these problems under Linux and Windows.

Is this an already known problem. Will it be fixed in LW 5?

Gerhard Weber