[XeTeX] error message in .bbl

[Nazareth Amlesom Kifle]

Hello,
Can anyone help me to understand the error I am getting in  
typesetting my bibliography. It used to work fine, but some reason I  
started to get the error message I am attaching below.  I haven't  
changed anything in my file.
What can be the problem, and how can i solve it.
Thank you in advance for you assistance.

Nazareth

] (./dissertation-master.bbl
Underfull \vbox (badness 10000) has occurred while \output is active []

  [289


]
Underfull \hbox (badness 1127) in paragraph at lines 81--84
[]\zf at basefont Arche, J. Mar\OT1/EthiopicLSU(0)/m/sc/10.95 ^^S^^P 
\zf at basefont a
. 2006. Individuals in time: tense, aspect and the indi-
  []


Underfull \vbox (badness 10000) has occurred while \output is active []

  [290]
Underfull \vbox (badness 10000) has occurred while \output is active []

  [291]
Underfull \hbox (badness 3590) in paragraph at lines 231--234
[]\zf at basefont Butt, Miriam, T. Holloway, King, Ni[]no, Maria-Eugenia  
and Segon
d,
  []


Underfull \vbox (badness 10000) has occurred while \output is active []

  [292]
Underfull \hbox (badness 4353) in paragraph at lines 273--275
[]\zf at basefont Comrie, Bernard. 1989. Language universals and  
linguistic typolo
gy.
  []


Underfull \vbox (badness 10000) has occurred while \output is active []

  [293]
Underfull \hbox (badness 1824) in paragraph at lines 317--319
[]\zf at basefont Donohue, Mark. 1996. Relative Clauses in Tunkan Besi:  
Grammatica
l
  []


Underfull \vbox (badness 10000) has occurred while \output is active []

  [294]
Underfull \hbox (badness 1509) in paragraph at lines 388--390
[]\zf at basefont Giv[]on, Talmy. 1976. Topic, Pronoun, and Grammatical  
Agreement.
  In
  []


Underfull \hbox (badness 1571) in paragraph at lines 424--426
[]\zf at basefont Haspelmath, Martin. 2004. Argument making in  
Ditransitive alignm
ent
  []


Underfull \vbox (badness 10000) has occurred while \output is active []

  [295]
Underfull \hbox (badness 6995) in paragraph at lines 443--445
[]\zf at basefont Hetzron, Robert. 1972. Ethiopian Semitic: Studies in  
Classificat
ion.
  []


Underfull \vbox (badness 10000) has occurred while \output is active []

  [296]
Underfull \vbox (badness 10000) has occurred while \output is active []

  [297]
Missing character: There is no ÃÅ in font EthiopicLSU/AAT!
Missing character: There is no ÃÅ in font EthiopicLSU/AAT!

Underfull \vbox (badness 10000) has occurred while \output is active []

  [298]
Underfull \vbox (badness 10000) has occurred while \output is active []

  [299]
Underfull \vbox (badness 10000) has occurred while \output is active []

  [300]
Underfull \hbox (badness 1337) in paragraph at lines 765--770
[]\zf at basefont Reid, Nicholas. 2000. Complex verb collectionss in  
Ngan'gityemer
ri: a
  []