Importing files in Integration Design

Hi,

This is new system.I am importing the ,tpz files in Integration Directory.I already imported 3 files and in the process of 4th files i got this error :

"Internal error: Unable to transfer changes for object Service | <SID>CLNT100 to change list "XI 3.0 Import" (****************************) since object still in change list "XI 3.0 Import" (*********************************) "

What could be the reason ?

Thanks

Venkat