java.util.zip.ZipException: Not in GZIP format 1.8.1 pre-4

when loading any worlds including new worlds minecraft instantly crashes. this has just recently happened as of today. yesterday i was able to play perfectly fine but since i closed it and relaunched it, it keeps crashing (crash report:not sure if this is right http://pastebin.com/NYKyJp4S ) I even tried to make new worlds but it keeps crashing anyways also.
2nd crash report from the launcher log (http://pastebin.com/9XdFPPEy)