Hi,
Something has obviously gone wrong, but you don't provide enough information to guess what. Let us read your error log more carefully.
Firstly, it complains that the org.w3c.sac/1.3.0.v20120820 plugin from D:\Java7\Workspace3\UpdateSite p2 repository has invalid file lib/flute.jar. It is noteworthy that the JAR which represents the org.w3c.sac/1.3.0.v20120820 bundle is for some reason located in a temporary directory. I don't know if this is how it should be or if it's wrong, but it looks a bit suspicious to me.
Then, Maven complains about an identical problem org.eclipse.nebula.widgets.nattable.core.feature/1.1.0.201405012245 with feature.
My guess is both the plugin and the feature jars in the temp directory are corrupted. Why they are corrupted is beyond me and depends on how they got there. Were they mirrored from a remote repo at
eclipse.org, from a local Nexus instance? Were they build by Tycho or Eclipse PDE? You don't tell anything. Finally, your description sounds like you didn't do anything and the build has broken, but this is improbable. What have you done since the last successful build? Any code modifications/cleanups/jdk reinstalls/git checkouts/ide updates? Has this configuration ever worked before at all?
I hope the process of getting answers for these questions would help you self or with list's help understand the problem's origin.