Excel File Corrupted

Hi ,
When i uploaded Excel file using DHTMLXVault , the file size is increased from 10kb to 50 kb &
Also got corrupted. when i try to open the excel file it pops up error message :

Excel found unreadable content in file . Do you want to recover the contents of this workBook ?

Please help .

Thanks
Satish

What server side language do you use?