Right now it's not possible to install Win Switch in any version Ubuntu. The dependecies say that you need at least xpra xpra 0.0.7.14 but only 0.0.6.0 is available in Ubuntu... YOu can check this by looking into... ​http://packages.ubuntu.com/search?keywords=xpra&searchon=names&suite=all&section=all

If you really need such a new version, you need to offer this version in your repos.

$ wget "http://winswitch.org/dists/gentoo/xpra-0.0.7.17.ebuild"
--2011-01-24 20:47:30--  http://winswitch.org/dists/gentoo/xpra-0.0.7.17.ebuild
Resolving winswitch.org... 194.145.197.105
Connecting to winswitch.org|194.145.197.105|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 566 [text/plain]
Saving to: `xpra-0.0.7.17.ebuild'

100%[======================================>] 566         --.-K/s   in 0s

2011-01-24 20:47:30 (21.6 MB/s) - `xpra-0.0.7.17.ebuild' saved [566/566]

$ ls /usr/local/portage/net-misc/xpra/
Manifest  xpra-0.0.7.16.ebuild
$ sudo cp xpra-0.0.7.17.ebuild /usr/local/portage/net-misc/xpra/
Password:
$ sudo rm -i /usr/local/portage/net-misc/xpra/*16*
rm: remove regular file `/usr/local/portage/net-misc/xpra/xpra-0.0.7.16.ebuild'? y
$ sudo ebuild /usr/local/portage/net-misc/xpra/*ebuild manifest
>>> Downloading 'http://gentoo.virginmedia.com/distfiles/xpra-0.0.7.17.tar.bz2'
--2011-01-24 20:51:46--  http://gentoo.virginmedia.com/distfiles/xpra-0.0.7.17.tar.bz2
Resolving gentoo.virginmedia.com... 194.117.143.69, 194.117.143.70, 194.117.143.71, ...
Connecting to gentoo.virginmedia.com|194.117.143.69|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2011-01-24 20:51:46 ERROR 404: Not Found.

...
>>> Downloading 'http://windowswitch.org/src/xpra-0.0.7.17.tar.bz2'
--2011-01-24 20:51:47--  http://windowswitch.org/src/xpra-0.0.7.17.tar.bz2
Resolving windowswitch.org... 194.145.197.105
Connecting to windowswitch.org|194.145.197.105|:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://winswitch.org//src/xpra-0.0.7.17.tar.bz2 [following]
--2011-01-24 20:51:47--  http://winswitch.org//src/xpra-0.0.7.17.tar.bz2
Resolving winswitch.org... 194.145.197.105
Reusing existing connection to windowswitch.org:80.
HTTP request sent, awaiting response... 200 OK
Length: 887754 (867K) [application/x-bzip2]
Saving to: `/usr/portage/distfiles/xpra-0.0.7.17.tar.bz2'

100%[======================================>] 887,754      251K/s   in 3.5s

2011-01-24 20:51:51 (250 KB/s) - `/usr/portage/distfiles/xpra-0.0.7.17.tar.bz2' saved [887754/887754]

>>> Creating Manifest for /usr/local/portage/net-misc/xpra
912 ~ $ sudo emerge -pv xpra

These are the packages that would be merged, in order:

Calculating dependencies... done!

!!! All ebuilds that could satisfy "xpra" have been masked.
!!! One of the following masked packages is required to complete your request:
- net-misc/xpra-0.0.7.17 (masked by: invalid: IUSE contains defaults, but EAPI doesn't allow them)

For more information, see the MASKED PACKAGES section in the emerge
man page or refer to the Gentoo Handbook.

$
$ eix -I portage$ --format '<installedversions:NAMEVERSION>'
sys-apps/portage-2.1.9.25
$

$ sudo emerge xpra
Password:
Calculating dependencies... done!

>>> Verifying ebuild manifests

>>> Emerging (1 of 1) net-misc/xpra-0.0.7.17 from unknown repo
 * xpra-0.0.7.17.tar.bz2 RMD160 SHA1 SHA256 size ;-) ...                 [ ok ]
 * Package:    net-misc/xpra-0.0.7.17
 * USE:  elibc_glibc kernel_linux server ssh userland_GNU x86
>>> Unpacking source...
>>> Unpacking xpra-0.0.7.17.tar.bz2 to /var/tmp/portage/net-misc/xpra-0.0.7.17/work
>>> Source unpacked in /var/tmp/portage/net-misc/xpra-0.0.7.17/work
>>> Compiling source in /var/tmp/portage/net-misc/xpra-0.0.7.17/work/xpra-0.0.7.17 ...
 * Building of net-misc/xpra-0.0.7.17 with CPython 2.6...
python2.6 setup.py build -b build-2.6
Traceback (most recent call last):
  File "setup.py", line 40, in <module>
    from Cython.Distutils import build_ext
ImportError: No module named Cython.Distutils
 * ERROR: net-misc/xpra-0.0.7.17 failed:
 *   Building failed with CPython 2.6 in distutils_building() function
 *
 * Call stack:
 *     ebuild.sh, line   56:  Called src_compile
 *   environment, line 4850:  Called distutils_src_compile
 *   environment, line 1258:  Called python_execute_function 'distutils_building'
 *   environment, line 3466:  Called die
 * The specific snippet of code:
 *                       die "${failure_message}";
 *
 * If you need support, post the output of 'emerge --info =net-misc/xpra-0.0.7.17',
 * the complete build log and the output of 'emerge -pqv =net-misc/xpra-0.0.7.17'.
 * This ebuild is from an overlay: '/usr/local/portage/'
 * The complete build log is located at '/var/tmp/portage/net-misc/xpra-0.0.7.17/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/net-misc/xpra-0.0.7.17/temp/environment'.
 * S: '/var/tmp/portage/net-misc/xpra-0.0.7.17/work/xpra-0.0.7.17'

>>> Failed to emerge net-misc/xpra-0.0.7.17, Log file:

>>>  '/var/tmp/portage/net-misc/xpra-0.0.7.17/temp/build.log'
$

Resolved with emerge -1 dev-python/cython-0.13

Not sure if this is a runtime or buildtime-only dep.