Input Method cursor does not move in Ubuntu using ibus

On Ubuntu 10.04 LTS with iBus it seems that QInputMethodEvent does not contain informations about the position of the cursor. I selected the Japanese-anthy input method in the ibus control panel and I can type Japanese in any QLineEdit (for example). When I use the arrows to move the cursor in the preedit string I obtain the correct result (that is the next insertion is where I expect it to be) but the cursor is always displayed at the end of the string. I can confirm also that QInputMethodEvent does not contain any information about the current cursor position (IM attributes are such that the cursor is at the end of the string and no selection information is contained in the text formatting attributes).