Updading/replacing existing sharepoint document in library

Hello!
 
Ive been strugling with a problem when replacing an existing document in SP document library (I need to change the contents of the file). Ive tried it in two ways:

spFile.File.SaveBinary(newData);
 
currSpWeb.Files.Add(destFile, memoryStream, true(overwrite))

 
in both cases the file contents are replaced and all, but the field "Title" (it has to stay the same) in the library is overwriten with an empty string.
 
Ive debuged it and before it exits the method the field is stil filled out correctly. But after it finishes, and if I go to the library the item appears with "Title" field empty.
All other fields are filled out as before.
I would appriciate any help.
 
Edit: This only happens with .docx type of documents, all others are working fine, the irony is that only doxc files are allowed
 
Thanks
B