My JB which I purchased in late Jan 2010 came with the .34 Firmware. It had no DRM support whatsoever. I only loaded up .35a2 because it gave ADE DRM support. I opted for the custom version which allows a serif font - supplied in the thread.
My JB never locked up. Even after doing the .35a(2).
I still have some of the issues that are experienced by both the JB and the ALP w/re to getting the wrong first page when opening a new book. That is resolved by just backing out and opening the book again using the "OK" button.
You could always try doing a "Restore to default" found in the "Settings" menu's. followed by a pressing and holding the "Reset" button for the slow count of 20-30. Then do a reboot and see if it locks up. If it does then take this opportunity to re-do the FW update.
Note: the "restore to Default" will screw up your adobe folder so take a backup first to your HDD. If not the FW install will restore it.
The other thing. Are the lock ups occurring with the same ebooks. I have had a few instances where downloading the ebook and replacing the first copy with a fresh copy has resolved some issues. Sometime getting the book from a different source (if possible) works as well. Sometimes issues are with a document and not the reader.
Keep your nested folders to three and under. More than three nested folders can cause problems.
I have an Alurateh (ALP) as well and it pretty well has the same issues w/re to getting a previous open books page up when opening another ebook.