I've had a look at this bug: its some pretty dire code in the section the reads your .fvwmrc.
I submit the following patch to fix the problem. Austin --- configure.c.old Fri Oct 20 16:48:44 1995 +++ configure.c Fri Oct 20 21:36:12 1995 @@ -1979,12 +1979,10 @@ /* Generate a temporary filename. Honor the TMPDIR environment variable, if set. Hope nobody deletes this file! */ - if ((vc=getenv("TMPDIR"))) { - strcpy(tmp_name, vc); - } else { - strcpy(tmp_name, "/tmp"); + if ((vc=getenv("TMPDIR")) == NULL) { + vc = "/tmp"; } - strcat(tmp_name, "/fvwmrcXXXXX"); + sprintf(tmp_name, "%s/fvwmrc.%05d", vc, getpid()); mktemp(tmp_name); if (*tmp_name == '\0')