I can't reproduce this problem. Please try to reinstall screenlets with pacman. Which desktop environment do you use?

Confirmed on 3 different Arch installs. All 64 bit, all current. All running xfce4 desktop. Amd/Nvidia, Intel/Radeon, Vbox.

Reinstalling librsvg and python2-rsvg for an unrelated problem has also fixed screenlets. Verified this on my vbox install per below.

[jeff@Arch2013p4vb ~]$ screenlets
cat: /etc/screenlets/prefix: No such file or directory

** (screenlets-manager.py:509): WARNING **: Trying to register gtype 'WnckWindowState' as enum when in fact it is of type 'GFlags'

** (screenlets-manager.py:509): WARNING **: Trying to register gtype 'WnckWindowActions' as enum when in fact it is of type 'GFlags'

** (screenlets-manager.py:509): WARNING **: Trying to register gtype 'WnckWindowMoveResizeMask' as enum when in fact it is of type 'GFlags'
Traceback (most recent call last):
File "/usr/share/screenlets-manager/screenlets-manager.py", line 1342, in <module>
app = ScreenletsManager()
File "/usr/share/screenlets-manager/screenlets-manager.py", line 88, in __init__
self.create_ui()
File "/usr/share/screenlets-manager/screenlets-manager.py", line 300, in create_ui
w.set_icon_list(icontheme.load_icon("screenlets", 24, 0))
glib.GError: Icon 'screenlets' not present in theme
[jeff@Arch2013p4vb ~]$ sudo pacman -S librsvg python2-rsvg
[sudo] password for jeff:
warning: librsvg-2.37.0-2 is up to date -- reinstalling
warning: python2-rsvg-2.32.0-12 is up to date -- reinstalling
resolving dependencies...
looking for inter-conflicts...

Packages (2): librsvg-2.37.0-2 python2-rsvg-2.32.0-12

Total Installed Size: 0.61 MiB
Net Upgrade Size: 0.00 MiB

:: Proceed with installation? [Y/n] y
(2/2) checking keys in keyring [#####################################] 100%
(2/2) checking package integrity [#####################################] 100%
(2/2) loading package files [#####################################] 100%
(2/2) checking for file conflicts [#####################################] 100%
(2/2) checking available disk space [#####################################] 100%
(1/2) reinstalling librsvg [#####################################] 100%
(2/2) reinstalling python2-rsvg [#####################################] 100%
[jeff@Arch2013p4vb ~]$ screenlets
cat: /etc/screenlets/prefix: No such file or directory

** (screenlets-manager.py:576): WARNING **: Trying to register gtype 'WnckWindowState' as enum when in fact it is of type 'GFlags'

** (screenlets-manager.py:576): WARNING **: Trying to register gtype 'WnckWindowActions' as enum when in fact it is of type 'GFlags'

** (screenlets-manager.py:576): WARNING **: Trying to register gtype 'WnckWindowMoveResizeMask' as enum when in fact it is of type 'GFlags'
File /home/jeff/.config/screenlets/config.ini not found
Auto-create autostart dir ...
Create autostarter for: Screenlets Daemon
Error in ScreenletsManager.connect_daemon: org.freedesktop.DBus.Error.ServiceUnknown: The name org.screenlets.ScreenletsDaemon was not provided by any .service files
Trying to launching screenlets-daemon ...
no daemon yet
checking for running daemon again ...
DAEMON FOUND - Ending timeout
DAEMON FOUND!
Quit!
[jeff@Arch2013p4vb ~]$

Then it was probably a bug in librsvg. Anyway, If anybody experience this problem in the future, then try to run the following command as root:
# gdk-pixbuf-query-loaders --update-cache

I'm seeing same issue

I still can't reproduce the problem. You could try to run the following commands as root:
# gtk-update-icon-cache -t -f usr/share/icons/hicolor
# gdk-pixbuf-query-loaders --update-cache

Or please report the problem to the upstream developers:
https://bugs.launchpad.net/screenlets