My Steam client did the same after download the 153mb update. It now refuses to start with the following output:

[mewt@minas-morgul ~]$ steam &
[1] 14051
[mewt@minas-morgul ~]$ Running Steam on arch rolling 64-bit
STEAM_RUNTIME is enabled automatically
Installing breakpad exception handler for appid(steam)/version(1371599823_client)
Installing breakpad exception handler for appid(steam)/version(1371599823_client)
Installing breakpad exception handler for appid(steam)/version(1371599823_client)
Installing breakpad exception handler for appid(steam)/version(1371599823_client)
unlinked 0 orphaned pipes
removing stale semaphore last operated on by process 12335 with name 0eBlobRegistryMutex_E27351F4053A0ABB3CF705C956798614
removing stale semaphore last operated on by process 12335 with name 0eBlobRegistrySignal_E27351F4053A0ABB3CF705C956798614
removing stale semaphore last operated on by process 12335 with name 0emSteamEngineInstance
removing stale semaphore last operated on by process 12335 with name 0eSteamEngineLock
Fontconfig error: "/etc/fonts/conf.d/10-scale-bitmap-fonts.conf", line 70: non-double matrix element
Fontconfig error: "/etc/fonts/conf.d/10-scale-bitmap-fonts.conf", line 70: non-double matrix element
Fontconfig warning: "/etc/fonts/conf.d/10-scale-bitmap-fonts.conf", line 78: saw unknown, expected number
Installing breakpad exception handler for appid(steam)/version(1371599823_client)
[0619/141639:WARNING:proxy_service.cc(958)] PAC support disabled because there is no system implementation
Installing breakpad exception handler for appid(steam)/version(1371599823_client)
Installing breakpad exception handler for appid(steam)/version(1371599823_client)
Installing breakpad exception handler for appid(steam)/version(1371599823_client)
Installing breakpad exception handler for appid(steam)/version(1371599823_client)
Installing breakpad exception handler for appid(steam)/version(1371599823_client)
Generating new string page texture 2: 48x256, total string texture memory is 49.15 KB
Generating new string page texture 3: 256x256, total string texture memory is 311.30 KB
Installing breakpad exception handler for appid(steam)/version(1371599823_client)
Installing breakpad exception handler for appid(steam)/version(1371599823_client)

** (steam:14145): WARNING **: replace_settings: error updating connection /org/freedesktop/NetworkManager/Settings/17 settings: (1) type

The connecting steam account dialog will remain there indefinitely. If alt-f4 is used to kill steam the following is output:

unlinked 2 orphaned pipes
CAsyncIOManager: 0 threads terminating. 0 reads, 0 writes, 0 deferrals.
CAsyncIOManager: 1467 single object sleeps, 0 multi object sleeps
CAsyncIOManager: 0 single object alertable sleeps, 2 multi object alertable sleeps
[2013-06-19 14:16:37] Startup - updater built Jun 18 2013 15:36:28
[2013-06-19 14:16:37] Opted in to client beta 'publicbeta' via beta file
Looks like steam didn't shutdown cleanly, scheduling immediate update check
[2013-06-19 14:16:37] Checking for update on startup
[2013-06-19 14:16:37] Checking for available updates...
[2013-06-19 14:16:38] Download skipped by HTTP 304 Not Modified
[2013-06-19 14:16:38] Error: Failed to verify package manifest.
[2013-06-19 14:16:38] Verifying installation...
[2013-06-19 14:16:38] Verification complete
Shutting down. . .
[2013-06-19 14:18:38] Shutdown

This bug just happened to me, I restart to go online, it looks like it connects, but is in offline mode. Last night it was working, haven't downloaded any updates AFAIK.