After 70 seconds the rhttp connection times out, which is by design (the chttp conneciton is kept alive by serverstatus). When a new request occurs, the following happens:
1)  handleAdvice is called from getRequestSink on the timeout error.
2) serverDisconnected notification is sent which causes slimBrowse to put up the spinny.
3) a reconnect happens after a 3 second timeout

I notice that after a much longer time the timeout doesn't happen. Perhaps that's because the connection is fully closed and the following never occurs:
		if type(v) == "userdata" and t.timeout > 0 and now - t.lastSeen > t.timeout then
			log:error("network thread timeout for ", t.task)
			t.task:addTask("inactivity timeout")
		end

I'll investigate that a bit more.

Dump:
20090728 15:53:11.873 DEBUG  applet.SlimBrowser - SlimBrowserApplet.lua:623 _performJSONAction(from:0, qty:200):
20090728 15:53:11.873 DEBUG  net.comet - Comet.lua:459 Comet {mysqueezebox.com}: request(function: 0x1747a5a0, reqid:13, 00:1e:c2:1e:0d:e1, amazon,items,0,200,menu:amazon,useContextMenu:1, priority:nil)
20090728 15:53:11.873 DEBUG  net.comet - Comet.lua:355 Sending pending request(s):
{ --[[table: 0x1747ab80]]
  { --[[table: 0x1747ac00]]
    id = 13,
    data = { --[[table: 0x1747ac60]]
      request = { --[[table: 0x1747abc0]]
        "00:1e:c2:1e:0d:e1",
        { --[[table: 0x174c4320]]
          "amazon",
          "items",
          0,
          200,
          "menu:amazon",
          "useContextMenu:1",
        },
      },
      response = "/220213Xcffcc56a7f654cbe078d5bc5bed9898fX1248796353Xf03f157d/slim/request",
    },
    channel = "/slim/request",
  },
}
20090728 15:53:11.897 ERROR  net.thread - NetworkThread.lua:146 network thread timeout for Task(SocketHttp {mysqueezebox.com_Request}(R))
stack traceback:
	...lay/src/squeezeplay/share/jive/net/NetworkThread.lua:146: in function '_timeout'
	...lay/src/squeezeplay/share/jive/net/NetworkThread.lua:187: in function <...lay/src/squeezeplay/share/jive/net/NetworkThread.lua:155>
	[C 0x5d1c4]: in function 'pcall'
	...lay/src/squeezeplay/share/jive/net/NetworkThread.lua:205: in function <...lay/src/squeezeplay/share/jive/net/NetworkThread.lua:194>
20090728 15:53:11.902 ERROR  net.http - SocketHttp.lua:486 SocketHttp {mysqueezebox.com_Request}:t_rcvHeaders.pump:inactivity timeout
stack traceback:
	...zeplay/src/squeezeplay/share/jive/net/SocketHttp.lua:486: in function 'pump'
	...ezeplay/src/squeezeplay/share/jive/net/SocketTcp.lua:192: in function 'readPump'
	...queezeplay/src/squeezeplay/share/jive/net/Socket.lua:161: in function <...queezeplay/src/squeezeplay/share/jive/net/Socket.lua:159>
20090728 15:53:11.902 INFO   net.comet - Comet.lua:818 Comet {mysqueezebox.com}: _getRequestSink error: inactivity timeout
20090728 15:53:11.902 INFO   net.comet - Comet.lua:998 Comet {mysqueezebox.com}: handleAdvice state=CONNECTED
20090728 15:53:11.902 DEBUG  net.comet - Comet.lua:547 Comet {mysqueezebox.com}: state is UNCONNECTED
20090728 15:53:11.902 INFO   squeezebox.server - SlimServer.lua:669 disconnected mysqueezebox.com idleTimeoutTriggered: nil
20090728 15:53:11.903 DEBUG  net.comet - Comet.lua:198 Comet {basementtv}: connect state=UNCONNECTED
20090728 15:53:11.903 DEBUG  net.comet - Comet.lua:568 Comet {basementtv}: _handshake(), calling: http://192.168.1.103:9000/cometd
20090728 15:53:11.903 DEBUG  net.comet - Comet.lua:580 Will re-subscribe to /slim/serverstatus
20090728 15:53:11.903 DEBUG  net.comet - Comet.lua:580 Will re-subscribe to /slim/firmwarestatus
20090728 15:53:11.903 DEBUG  net.comet - Comet.lua:547 Comet {basementtv}: state is CONNECTING
20090728 15:53:11.903 DEBUG  net.comet - Comet.lua:198 Comet {Tom Wadzinski’s MacBook Pro}: connect state=UNCONNECTED
20090728 15:53:11.903 DEBUG  net.comet - Comet.lua:568 Comet {Tom Wadzinski’s MacBook Pro}: _handshake(), calling: http://192.168.1.106:9000/cometd
20090728 15:53:11.903 DEBUG  net.comet - Comet.lua:580 Will re-subscribe to /slim/serverstatus
20090728 15:53:11.903 DEBUG  net.comet - Comet.lua:580 Will re-subscribe to /slim/firmwarestatus
20090728 15:53:11.903 DEBUG  net.comet - Comet.lua:547 Comet {Tom Wadzinski’s MacBook Pro}: state is CONNECTING
20090728 15:53:11.904 DEBUG  net.comet - Comet.lua:198 Comet {Kitchen-Netbook}: connect state=UNCONNECTED
20090728 15:53:11.904 DEBUG  net.comet - Comet.lua:568 Comet {Kitchen-Netbook}: _handshake(), calling: http://192.168.1.149:9000/cometd
20090728 15:53:11.904 DEBUG  net.comet - Comet.lua:580 Will re-subscribe to /slim/serverstatus
20090728 15:53:11.904 DEBUG  net.comet - Comet.lua:580 Will re-subscribe to /slim/firmwarestatus
20090728 15:53:11.904 DEBUG  net.comet - Comet.lua:547 Comet {Kitchen-Netbook}: state is CONNECTING
20090728 15:53:11.904 INFO   applet.SlimBrowser - SlimBrowserApplet.lua:2498 _problemConnectingPopup
20090728 15:53:11.906 ERROR  net.comet - Comet.lua:1039 Comet {mysqueezebox.com}: advice is retry, connect in 3.163 seconds
stack traceback:
	...squeezeplay/src/squeezeplay/share/jive/net/Comet.lua:1039: in function <...squeezeplay/src/squeezeplay/share/jive/net/Comet.lua:997>
	(tail call): ?