zone: PV ENTRY(0xc1033000) slab 0xc8374da0 freed address 0xc83747e8 unaligned

Everytime I run "make buildworld", I get the same lines and find myself
in the debug-prompt.

Here is my uname -a:
FreeBSD baustelle.otfa.local 5.3-BETA3 FreeBSD 5.3-BETA3 #0: Sun Sep  5
15:58:07 CEST 2004    
root_at_baustelle.otfa.local:/usr/obj/usr/src/sys/GENERIC  i386


And here are the last lines of output:

zone: PV ENTRY(0xc1033000) slab 0xc8374da0 freed address 0xc83747e8
unaligned. panic: should be 0xc83747e0

cpuid = 0
KDB: enter: panic
[thread 100096]
Stopped at kdb_enter+0x2b: nop

db>tr

kdb_enter(c07f099b) at kdb_enter+0x2b
panic(c080a2fe,c83747e0,c080a2cc,c080f4bb,c1033000) at panic+0x127
uma_dbg_free(c1033000,0,c83747e8) at uma_dbg_free+0xa4
uma_zfree_arg(c1033000,c83747e8,0) at uma_zfree_arg+0xf3
pmap_remove_entry(c15e1da4,c10d5278,962b000,962b000,9800000) at
pmap_remove_entry+0x106 pmap_remove_pte(c15e1da4,bfc258ac,962b000) at
pmap_remove_pte+0xda pmap_remove(c15e1da4,8068000,995e000) at
pmap_remove_+0x106 vm_map_deöete(c15e1ce4,8068000,995e00) at
vm_map_delete+0x159 obreak(c1d56b00,cd940d14,1,12,287) at obreak+0x1a9
syscall(2f,2f,2f,9959000,8055060) at syscall+0x213
Xint0x80_syscall() at Xint0x80_syscall+0x1f
--- syscall (17, FreeBSD ELF32, obreak), eip = 0x280d883b, esp =
0xbfbfe93c, ebp = 0xbfbfe978 --- 
db>

I used an unmodified 5.2.1-p9 GENERIC-System and upgraded it without
errors. The sources are from about 11:30 today (Sunday 05.09.2004).