Nuget - unable to resolve package that could previously be resolved

We have a nuget server set up and are using Jenkins for CI integration. For the past two months everything has been working perfectly, however today we got the following error after update one of our Nuget packages:

Jenkins\Trunk\trunk\Solution.sln" (default target) (1) -> "F:\Jenkins\Trunk\trunk\Ioc\TPI.csproj" (default target) (44) -> F:\Jenkins\Trunk\trunk.nuget\NuGet.targets(100,9): error : Unable to find version '1.0.3.2' of package 'Solution.Extensions'. [F:\Jenkins\Trunk\trunk\Ioc\TPI.csproj]

I checked our nuget server and the package is definitely there. Previous versions have resolved fine, however this latest update and publish of our package seems to have inexplicably broken something. It was a simple update to the nuget package, just a single method being added with no dependencies created and the tried and tested publish procedure followed.

Any ideas why MS Build might suddenly be unable to resolve a Nuget dependency? All suggestions welcome.

Thanks