With debug and verbose tracing enabled, printing code can be seen in the trace messages if one navigates away from the applet by clicking on another tab.
Problem can be reproduced on XP with IE7.
Steps:
- open IE7
- have at least 2 tabs enabled in the same browser window
- load a simple applet in one tab
- click on another tab

The trace messages seen at the Java console and at the dos console are as follows:

From java console:
-----
Applet Status: Applet started
Applet Status: Told clients applet is started
PluginMain: processing SetAppletSizeMessage
PluginMain: setting size of applet 2 to (400, 400)
PluginMain: processing PrintAppletMessage
PluginMain: printing applet 2 isPrinterDC = false
PluginMain: processing PrintAppletMessage
PluginMain: printing applet 2 isPrinterDC = false
PluginMain: processing HeartbeatMessage
PluginMain: processing HeartbeatMessage
------


From dos console:
---------
IExplorerPlugin.SetObjectRects(cAxControl = 0x3712678, left = 12, right = 412, t
op = 67, bottom = 467)
IExplorerPlugin.OnDraw(cAxControl = 0x3712678)
JVMInstance for 1.6.0.10 sending print applet message for applet ID 2, HDC = 147
6465775, isPrinterDC = false
JVMInstance (1.6.0.10) processing PrintBandMessage
JVMInstance (1.6.0.10) processing PrintBandMessage
JVMInstance (1.6.0.10) processing PrintBandMessage
JVMInstance (1.6.0.10) processing PrintBandMessage
JVMInstance (1.6.0.10) processing PrintBandMessage
JVMInstance (1.6.0.10) processing PrintBandMessage
IExplorerPlugin.OnDraw(cAxControl = 0x3712678)
JVMInstance for 1.6.0.10 sending print applet message for applet ID 2, HDC = 147
6465775, isPrinterDC = false
JRE 1.6.0.10: [GC 2201K->1451K(5056K), 0.0030169 secs]
JVMInstance (1.6.0.10) processing PrintBandMessage
JVMInstance (1.6.0.10) processing PrintBandMessage
JVMInstance (1.6.0.10) processing PrintBandMessage
JVMInstance (1.6.0.10) processing PrintBandMessage
JVMInstance (1.6.0.10) processing PrintBandMessage
JVMInstance (1.6.0.10) processing PrintBandMessage
----------