yum errors

[gaurav <gauravp hclcomnet co in>]

hi list,
I am facing getting lot errors while using yum (lots of HTTP Error 400) 
and in end I get IndexError: list index out of range

why its happening ....

xorg-x11-libs-6.8.2-1.FC3 100% |=========================| 277 kB    00:25
---> Package xorg-x11-libs.i386 0:6.8.2-1.FC3.13 set to be updated
---> Downloading header for gamin to pack into transaction set.
http://www.las.ic.unicamp.br/pub/fedora/linux/core/updates/3/i386/gamin-0.0.25-1.FC3.i386.rpm: 
[Errno 4] IOError: HTTP Error 400: Bad Request ( The data is invalid.  )

http://www.las.ic.unicamp.br/pub/fedora/linux/core/updates/3/i386/gamin-0.0.25-1.FC3.i386.rpm: 
[Errno 4] IOError: HTTP Error 400: Bad Request ( The data is invalid.  )
Trying other mirror.
Traceback (most recent call last):
 File "/usr/bin/yum", line 8, in ?
   yummain.main(sys.argv[1:])
 File "/usr/share/yum-cli/yummain.py", line 104, in main
   (result, resultmsgs) = base.buildTransaction()
 File "/usr/lib/python2.3/site-packages/yum/__init__.py", line 174, in 
buildTransaction
   (rescode, restring) = self.resolveDeps()
 File "/usr/lib/python2.3/site-packages/yum/depsolve.py", line 148, in 
resolveDeps
   self.populateTs(test=1)
 File "/usr/lib/python2.3/site-packages/yum/depsolve.py", line 106, in 
populateTs
   self.downloadHeader(po)
 File "/usr/lib/python2.3/site-packages/yum/__init__.py", line 454, in 
downloadHeader
   end=end, checkfunc=checkfunc, copy_local=1)
 File "/usr/lib/python2.3/site-packages/yum/repos.py", line 443, in get
   checkfunc=checkfunc)
 File "/usr/lib/python2.3/site-packages/urlgrabber/mirror.py", line 
414, in urlgrab
   return self._mirror_try(func, url, kw)
 File "/usr/lib/python2.3/site-packages/urlgrabber/mirror.py", line 
392, in _mirror_try
   mirrorchoice = self._get_mirror(gr)
 File "/usr/lib/python2.3/site-packages/urlgrabber/mirror.py", line 
290, in _get_mirror
   return gr.mirrors[gr._next]
IndexError: list index out of range