Tray icon unresponsive when started in "keepuptodate" mode

When running WinSCP with the "/keepuptodate" flag, the synchronization dialog box shows up as expected. After starting the synchronization the dialog box can be minimized to tray. After some while, of about 10 minutes, the tray icon becomes unresponsive. The synchronization itself, does keep on working the whole time. This makes it impossible to stop synchronization or exit WinSCP without killing the process.

Running WinSCP 5.5.3 (build 4214)
Windows 7, 64-bit, SP 1

WinSCP was started from command line using:
"C:\Program Files (x86)\WinSCP\WinSCP.exe" "stav@mcluster03" /keepuptodate S:\Dropbox\Projects\GlassFree /home/stav/GlassFree

"stav@mcluster03" is one of my saved sessions which uses SFTP and includes a pre-entered password. All other connection parameters are default.

Can you think of any even that may trigger this problem? Like does it happen after the first update (upload) or similar?

While testing this, I found and fixed related problem. I have sent you an email with a development version of WinSCP to address you have used to register on this forum. Please test in, in case it resolves your problem too.

Thanks for your quick reply and I'm sorry for my (very) late reply.

I think I managed to isolate one condition that triggers this - when an upload happens a popup window with progress is displayed (even when WinSCP is minimized to tray). I think, by the way, that a nice UI enhancement is to have these popups "Dropbox style" when minimized (i.e. a small balloon near the tray icon). But, as per my bug report, if I cancel the upload while in progress then the behaviour described below is apparent: the GUI is no longer responsive but synchronization continues properly.

While testing this I noticed another problem (I can post a different thread if you require): When starting WinSCP using the command line in the original post I get a window for selecting options. If I unselect "Subdirectories" (the rest of the options default) and start synchronizing then the initial sync works properly. However, after the first upload it immediately starts syncing the subdirectories.

Thanks for your help!
I'm a great fan of your software!

(P.S. I did not receive your mail with the dev version and so have not tested it. I think the forum has my correct address since I get notification mails)

Progress windows should not be popping up when WinSCP is minimized to tray. It can be related to your problem.

Anyway, I have resent the email with dev version.