SSIS Package Failed to lock variable

Hi..

I have developed one package that will zip the file naming with current date and upload it to ftp..

The file zip task is done..but i can't upload the created zip file with today's date to ftp.

For. e.g. I have one file Order.mdb

Now i am zipping it by date e.g Order_08_26_2013.zip

this name will be created at runtime using expressions.

But now i am uploading the same file on ftp using runtime expression on FTP task as below

@[User::FullFilePathZip] +"_"+  REPLACE((DT_WSTR, 30) (DT_DBDATE) GETDATE(),"-","_")  + ".zip"

the value of evaluated expression is same as zipped file name..But it says "Failed to lock variable....."

Please find attached screen shot for detail. http://social.msdn.microsoft.com/Forums/getfile/324467