psabackup is not working anymore

[knocx]

we had an automated plesk backup system working perfectly on 8.0.1 but after upgraded to 8.1.0 3 weeks ago it all broke down

when we backup with verbose option

it hangs at

Phase 2/2: packing data

but continues generating the splitted backup files .001 .002 ...etc

after a time process is dead / killed somehow

and prompt is still Phase 2/2: packing data

we also tested non-split / single file option nothing changes

Current PLESK is all patched including hotfix3

any ideas?
knocx