ODesk client is verified against viruses and such threats because the server you are downloading from is protected against such things and the client is verified. The stake is to big to implement viruses into Odesk client because the file comes from a respected company which it's in the online business for years . It's most likely possible that you downloaded the file with the virus from a 3rd party website which has no connection to the main one but it acts as it was somewhat related to the original one.
My recommendation is to try and download the client from its official location. On the other side, the client isn't available publicly because you have to log in into your members area in order to download it.
