guest connection lost

[Guy_Przytula]

host : windows 7 64b
vbox:4.3.12.R93733 (not latest version but other issue R module....and still not resolved for me)
having ubuntu 12.4.02 4b
guest with nat and hoa : all ok - internet access and pinging host (working for some time)
after a system restart : I can not ping the guest anymore although can still ping the host
Pinging 192.168.56.101 with 32 bytes of data:
Request timed out.
ipconfig :
Ethernet adapter VirtualBox Host-Only Network:

Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80:3652:f627:4a80%36
Autoconfiguration IPv4 Address. . : 169.254.74.128
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :
This was working fine for me : I can't remember having changed any setting (host or guest) just installing software in guest and using it through putty...
Any idea/help would be welcome
thank for all update : best regards
Guy Przytula

[Guy_Przytula]

sorry for coming back
after some system restart (windows) and starting guest same problem occurred again
no ping to guest - ping guest to host=ok
any idea what could be the reason ?
trying booting host-guest and finally getting connection again
best regards, Guy Przytula