Thanks for your reply.  The following appeared when I tried to launch the application again this morning:
13/12/2011 09:47:37	[0x0-0x11f11f].com.spotify.client[2235]	09:47:37.431 I [breakpad.cpp:36] Registered Breakpad for product: spotify
13/12/2011 09:47:37	[0x0-0x11f11f].com.spotify.client[2235]	09:47:37.458 I [translate.cpp:123] Reloading all languages
13/12/2011 09:47:37	Spotify[2235]	*** __NSAutoreleaseNoPool(): Object 0xb0d590 of class NSCFString autoreleased with no pool in place - just leaking
13/12/2011 09:47:37	Spotify[2235]	Reachability Flag Status: -R -----l- networkStatusForFlags
13/12/2011 09:47:37	[0x0-0x11f11f].com.spotify.client[2235]	09:47:37.673 I [breakpad.cpp:94] Searching for crashdumps: /Users/aruback/Library/Caches/com.spotify.client/*.dmp
13/12/2011 09:47:37	Spotify[2235]	Frame: {{104, 62}, {290, 28}}
13/12/2011 09:47:39	[0x0-0x11f11f].com.spotify.client[2235]	09:47:39.727 I [breakpad.cpp:105] Not allowed to upload file
13/12/2011 09:47:53	[0x0-0x11f11f].com.spotify.client[2235]	09:47:53.549 I [user_cache:138] UserCache::initiateGetUsers() will query for 1 users
13/12/2011 09:47:53	[0x0-0x11f11f].com.spotify.client[2235]	09:47:53.756 I [ap:1754] Connecting to AP B5.spotify.com:4070
13/12/2011 09:47:53	[0x0-0x11f11f].com.spotify.client[2235]	09:47:53.841 I [mainview:6276] onAppActivate(1)
13/12/2011 09:47:53	[0x0-0x11f11f].com.spotify.client[2235]	09:47:53.909 I [mainview:6999] Load complete (0) url: about:blank
Is there a clue in here as to the problem?