Hi Husain,
In order to upload files to VEAccess you have to have a client certificate installed to validate you against VEacces, this will download autmoatically when you try to upload a file the fiirst time..
Can you open SAP Visual Enterprise Generator Configuration and click on the Seucirty tab? It should tell you if your farm certificate is valid or not. You will have to be logged into the server with the same user name you where logged in as when you installed the software.
also check the licensed tab to make sure VEG is still being seen as licensed.