Since kde-4.8.1 (maybe even 4.8.0) I cannot use the right mouse button (RMB) on an application that also uses mouse gestures. I've just updated to KDE-4.8.3 and this issue is till here.

For example, I've set up Konqueror (systemsettings > shortcuts and gestures) to use mouse gestures with the RMB. Mouse gestures work as expected, but I can not open the RMB-menu anymore (the menu where I can cut/copy/paste selected text).

Before KDE-4.8.1 or 4.8.0 the use of mouse gestures didn't disable the other activities of the RMB: mouse gestures with the RMB work and opening the RMB-menu also work.

I've submitted a bug report (https://bugs.kde.org/show_bug.cgi?id=297667), but no replies from others/developers there yet.

Anyone here have the same problem?
Is there something I can try to make this work again?

This occurs on a new user I take it? (after configuring it appropriately of course)

Yes, this happens with a new user.
I have a user named 'test' for this situations. I've deleted the /home/test and the kdecache-test directories. Logged in, enabled mouse gestures with mouse button number 3 (right mouse button), started Konqueror...
The result is the same: mouse gestures work, but right mouse button menu cannot be opened.

Something I didn't mention in my opening post:
1) Both mouse gestures and opening right mouse menu work when Konqueror's window is inactive, ofcourse after the gesture or opening the menu the window is activated.
2) There is a work-around to open the right mouse menu: press the left mouse button (keep it pressed) and then click on (press and release) the right mouse button, the menu will appear and then the left mouse button can be released.

Ok, please file a bug at bugs.kde.org. It seems that a regression may have occurred with regard to mouse gestures.