What is wrong with Quartus II?

In case this could remind something to someone who knows the issue and, above all, who knows how to fix it:

The problem occurs exclusively after a QSYS generate.

I indeed spent the whole day debugging and compiling dozens of time the same project and Quartus has always been responsive.

Up to when I had to regenerate the design because it was no more fitting in the device and I thus had to change some settings in QSYS...

Now it takes again minutes to give back hand to any command... ?!?

My feeling is that Quartus detected that something was changed, and tries to find out what...

But why is this so long? Even sometimes requires that Quartus need to be killed in order to continue...?

Thanks

-jylo