Mac OS 10.8.5 PPTP VPN can't ping hosts few minutes

I connect to PPTP VPN from my MPA and get very strange behavior. VPN connect without any errors, but after connection I can't reach any host from VPN-network about three minutes. After that everything is fine.

When I ping host from VPN-network I get:

Request timeout for icmp_seq *

And sometimes, rarely:

ping: sendto: No buffer space available

In the end of ppp.log file I can see something like that:

Sat Jan 10 01:52:21 2015 : sent [IP data <src addr ip> <dst addr 255.255.255.255> <BOOTP Request> <type INFORM> <client id 0x08000000010000> <parameters = 0x6 0x2c 0x2b 0x1 0xf9 0xf>]
Sat Jan 10 01:52:24 2015 : No DHCP server replied

(not sure it is important)

Why is this happening and how to fix it?

Maybe it will be useful:

uname -a
Darwin air.local 12.5.0 Darwin Kernel Version 12.5.0: Sun Sep 29 13:33:47 PDT 2013; root:xnu-2050.48.12~1/RELEASE_X86_64 x86_64