No sound from Playback() and Background()

I have ubuntu 11.04 and Asterisk 1.8 on virtual server in cloud with static ip. Everything worked fine, but 2 weeks ago stopped working IVR. Apps Playbak and Background just dont work. Dial plan stuсks on steep 3 and does nothing
In console i have
Verbosity is at least 5
== Using SIP RTP CoS mark 5
– Executing [3000@office:1] Wait(“SIP/1001-0000000d”, “0.5”) in new stack
– Executing [3000@office:2] Answer(“SIP/1001-0000000d”, “”) in new stack
– Executing [3000@office:3] Playback(“SIP/1001-0000000d”, “/usr/share/asterisk/sounds/en_US_f_Allison/demo-instruct”) in new stack
– <SIP/1001-0000000d> Playing ‘/usr/share/asterisk/sounds/en_US_f_Allison/demo-instruct.gsm’ (language ‘en’)

No errors. File is OK 100% playable, cheked on other server. Voice and calls goes without problems.
After reinstallation of the whole system, tested on clear configuration same result.
sip.conf
[1001]
type=friend
username=1001
secret=*****
nat=yes
host=dynamic
transfer=yes
context=office
qualify=yes

extensions.conf
[office]
exten => 3000,1,Wait(0.5)
exten => 3000,2,Answer
exten => 3000,3,Playback(/var/lib/asterisk/sounds/en/demo-instruct)
exten => 3000,4,Hangup

Please help to find the solution.

Try this and let me know if Asterisk play the file :

[office]
exten => 3000,1,Answer()
exten => 3000,2,Playback(demo-thanks)
exten => 3000,3,Hangup()