为什么每次apt-get install automake都失败？ 是我的源list设定的问题吗？

[dos5gw]

安装automake失败， 无论apt-get install automake或者加上－－fix－missing参数，都无法安装automake。
apt-get install automake失败提示：E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
apt-get install automake --fix-missing失败提示：Failed to fetch http://ubuntu.cn99.com/ubuntu/pool/main ... -1_all.deb 500 ( The request was rejected by the HTTP filter. Contact your ISA Server administrator. )

由于用的公司的光纤，网管可能会屏蔽一些网站，上面的意思是不是指这个意思？
还是我的 /etc/apt/sources.list有问题？


root@cir2633-laptop:/dos/linux/x86-qtopia# sudo apt-get install automake
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
automake
0 upgraded, 1 newly installed, 0 to remove and 2 not upgraded.
Need to get 559kB of archives.
After this operation, 1,819kB of additional disk space will be used.
Err http://ubuntu.cn99.com karmic/main automake 1:1.11-1
500 ( The request was rejected by the HTTP filter. Contact your ISA Server administrator. )
Failed to fetch http://ubuntu.cn99.com/ubuntu/pool/main ... -1_all.deb 500 ( The request was rejected by the HTTP filter. Contact your ISA Server administrator. )
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

root@cir2633-laptop:/dos/linux/x86-qtopia# sudo apt-get install automake --fix-missing
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
automake
0 upgraded, 1 newly installed, 0 to remove and 2 not upgraded.
Need to get 559kB of archives.
After this operation, 1,819kB of additional disk space will be used.
Err http://ubuntu.cn99.com karmic/main automake 1:1.11-1
500 ( The request was rejected by the HTTP filter. Contact your ISA Server administrator. )
Failed to fetch http://ubuntu.cn99.com/ubuntu/pool/main ... -1_all.deb 500 ( The request was rejected by the HTTP filter. Contact your ISA Server administrator. )

[lainme]

好像被屏蔽了……换个源吧