Quartus II Crashes -- Need Help!

My apologies for launching another thread, but I'm running out of options and cannot find help anywhere. I have tried searching this Forum, the Altera Site, Forums & Wiki, all to no avail. So I am trying again, with some additional info on the problem.

I am running Quartus II 32-bit Version 12.0 Build 263 08/02/2012 Web Edition,

with Service Pack Installed: 2

on Windows 7.

I am using schematic design entry in the Block Editor. I create a new design and compile it without problems. I then make a simple edit, for example re-naming a pin or instance, save the file, and attempt to compile again, and it crashes. In addition:

Never crashes on first compile after starting

Does not crash if previous compile failed.

Editing connections does not cause crash

Sometimes crashes after Save All, and then attempt to exit.

Rebooting my PC makes no difference.

The crash report window says:

Internal Error: Sub-system: DBMUI, File: /quartus/db/dbmui/dbmui_manager.cpp, Line: 1152

Attempt made to free all hierarchy databases but the following callers are still accessing it: GEDQ_VIEW::get_sld_hdb_iname, GEDQ_VIEW::get_sld_hdb_iname

Stack Trace:

0x61c9: DBMUI_MANAGER::close_hdb_all_cap_inst + 0x109 (DB_DBMUI)

...... followed by lots more stack trace lines

Looking in directory

C:/altera/12.0sp2/quartus

I can see that there is no directory named "db",

and in the local design directory looking in "db", there is no

directory named "dbmui".

So the above crash report does not make much sense.

This being the free web version, I cannot expect direct help from Altera (although I'd willingly pay them for help if that were possible), and purchasing a licence is way beyond my resources as a hobbyist.

If I can't resolve this I'll have to abandon my plans to use CPLD/FPGA parts.

(and I'd be very reluctant to start all over again with Xilinx.)

Many thanks for any help you can offer. Ken.