I'm not sure what is wrong with either my .minecraft or if its the launcher but here it goes. Yesterday I was updating a mod and I thought I messed it up. When I would try to start up minecraft it would finish but the launcher would stay up and the game wouldn't launch. I ended up deleting everything that had to do with minecraft, forge and the mod (pixelmon 3.0.4) and starting from scratch redownloading everything. Yet even when I redownloaded it the same thing would happen where I couldn't play the 1.6.4 forge or 1.6.4 yet I could play more current versions such as 1.7.5 and 1.7.4. So I looked in the Development Console and found this:

[14:18:59 INFO]: Reconstructing virtual assets folder at C:\Users\Christina\AppData\Roaming\.minecraft\assets\virtual\legacy

[14:18:59 ERROR]: Couldn't unpack natives!

java.io.FileNotFoundException: Source 'C:\Users\Christina\AppData\Roaming\.minecraft\assets\objects\ad\ad126e435cca94054bf0d616301799a105526cde' does not exist
at org.apache.commons.io.FileUtils.copyFile(FileUtils.java:1074) ~[launcher.jar:?]
at net.minecraft.launcher.GameLauncher.reconstructAssets(GameLauncher.java:359) ~[launcher.jar:?]
at net.minecraft.launcher.GameLauncher.launchGame(GameLauncher.java:223) [launcher.jar:?]
at net.minecraft.launcher.GameLauncher.onDownloadJobFinished(GameLauncher.java:627) [launcher.jar:?]
at net.minecraft.launcher.updater.download.DownloadJob.popAndDownload(DownloadJob.java:120) [launcher.jar:?]
at net.minecraft.launcher.updater.download.DownloadJob.access$000(DownloadJob.java:12) [launcher.jar:?]
at net.minecraft.launcher.updater.download.DownloadJob$1.run(DownloadJob.java:89) [launcher.jar:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.7.0_51]
at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.7.0_51]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [?:1.7.0_51]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [?:1.7.0_51]
at java.lang.Thread.run(Unknown Source) [?:1.7.0_51]

and it just stops there, I haven't moved any files and not being tech savvy I'm not sure what it means or what's wrong. Any fixes to this?