Cannot find package

[Digital Ninja]

While installing flash player through GDebi installer, an error occured saying not all required files could be downloaded. Missing file is:
http://security.ubuntu.com/ubuntu/pool/main/n/nss/libnss3-dev_3.12.3.1-0ubuntu0.9.04.1_i386.deb

After browsing the /nss folder, I found a file called libnss3-dev_3.12.3.1-0ubuntu0.9.04.2_i386.deb

How can I tell Ubuntu to include that file insted, because it's obviously (a new version of) the same file.

[Partyboi2]

Hi, make sure you update the package list first

sudo apt-get update
If that does not work try changing your download server under Software Sources (System>Admin>Software Sources)