upload using single upload failed, multiple upload works :
Increase the maximum upload size
1. Click Start, point to All Programs, point to Administrative Tools, and then click SharePoint Central Administration.
2. Under Virtual Server Configuration, click Configure virtual server settings.
3. On the Virtual Server List page, click the virtual server you want to change.
4. On the Virtual Server Settings page, under Virtual Server Management, click Virtual server general settings.
5. Under maximum upload size, type the maximum file size (in MB) that you want to allow to be uploaded.
6. Click OK.
If IIS is timing out when you upload large files, you can configure the Connection timeout setting in IIS to allow more than the default 120 seconds (2 minutes).
Tune the IIS connection timeout
1. Click Start, point to All Programs, point to Administrative Tools, and then click Internet Information Services (IIS) Manager.
2. Right-click the virtual server you want to configure, and then click Properties.
3. Click the Web Site tab.
4.In the Connections section, in the Connection timeout box, type the number of seconds you want IIS to wait before timing out.
5. Click OK.