Right click and use save as to save the package on the HD then move the package to the cache directory and try to install from there I have never used kpackage but I would image it is not trying to force an overwrite it is just trying to install normally.
Thanks for trying to help me. I did that, and put the file in /var/cache/apt/archives. I then did "apt-get -f install", but got the same error. I'm thinking the problem doesn't have to do with the package and has to do with "/usr/X11R6/include/X11/Xcursor/Xcursor.h'".

apt-get -f install
Reading Package Lists... Done
Building Dependency Tree... Done
Correcting dependencies... Done
The following extra packages will be installed:
libxcursor-dev (1.0.2-2)
The following NEW packages will be installed:
libxcursor-dev (1.0.2-2)
0 upgraded, 1 newly installed, 0 to remove and 80 not upgraded.
7 not fully installed or removed.
Need to get 0B/27.3kB of archives.
After unpacking 135kB of additional disk space will be used.
Do you want to continue? [Y/n] Y
(Reading database ... 113340 files and directories currently installed.)
Unpacking libxcursor-dev (from .../libxcursor-dev_1.0.2-2_i386.deb) ...
dpkg: error processing /var/cache/apt/archives/libxcursor-dev_1.0.2-2_i386.deb (--unpack):
trying to overwrite `/usr/X11R6/include/X11/Xcursor/Xcursor.h', which is also in package xlibs-dev
Errors were encountered while processing:
/var/cache/apt/archives/libxcursor-dev_1.0.2-2_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)