Dump/snapshot problems

[Eugene]

Hi people,

Sometimes I have strange problems with dump -- or, rather, with snapshot it 
makes.
System is FreeBSD 5.3, default kernel configuration

Two types of problems:
1) System hangs or at least not accessible over the network and has to be 
physically reset. Last message on console
Collecting pv entries -- suggest increasing PMAP_SHPGPERPROС
maxproc limit exceeded by id(0), please see tuning(7) and login.conf(5)

Question: what exactly should I tune?

2) Dump process dies with message
mksnap_ffs: Cannot create //.snap/dump_snapshot: Resource temporarily 
unavailable
dump: Cannot create //.snap/dump_snapshot: No such file or directory

dmesg message
fsync: giving up on dirty: 0xc57b5d68: tag devfs, type VCHR, usecount 60263, 
writecount 0, refcount 960, flags (VV_OBJBUF), lock type devfs: EXCL (count 
1) by thread 0xc610f7d0 (pid 87575)
dev ad4s1a

What is wrong?

Thanks in advance
Eugene