If there’s no Source Control at play here, I’d do your import of 1 topic at a time (saving as you go) to discover the “bad” topic that’s causing the wheels to fall off.
We use Tortise SVN for version control. but that's never been an issue in the past. Short of rebuilding a 500+ topic project file by file, is there anything else I can try?
Then I might suspect some topics getting hung up in the source control – I’d check out the whole project and remove it from source control and see if it opens at that point. If it does, then you can check the whole thing back in as a fresh start; if it doesn’t, then you’re faced with rebuilding it piece by piece I’m afraid.
If after breaking the source control link you still have a problem, generate a CHM file to force an HHP file update.
Then open the project using the HHP file instead of the XPJ file. That might correct the problem but no guarantees.
See Opening Projects on my site for more detail of that method.
See www.grainge.org for RoboHelp and Authoring tips
Also using 220.127.116.111, I had exactly the same problem: open project, double-click a topic in the Topic List pane... crash.
However, immediately after opening the project I had Windows 7's blue 'busy' doughnut symbol constantly flashing under the mouse pointer. This is described (for RH8) in Peter Grainge's description on his excellent website (RoboHelp > Opening RoboHelp Projects). The same topic mentions the .hhp file, so I checked the contents of mine...
At the very end, in the [MERGE FILES] section, it listed two other .chm files; one which was supposed to be there, and one which was not (Dummy.chm). I had merged Dummy.chm only during the early testing stages of my project, and had long since removed all references to it from my project. I have no idea why it was still listed in the .hhp file.
I deleted the reference to Dummy.chm from the .hhp file and regenerated the project... and Dummy.chm reappeared in the .hhp file! After deep-searching my project files using NotePad++, one remaining reference to Dummy.chm was also listed in the .xpj file:
So I manually removed those lines and saved the .xpj using NotePad++, reopened the project using RoboHelp, and regenerated. The rogue reference to Dummy.chm is now gone. I have opened, saved, and closed the project several times and it now seems to be reliable.
Probable cause of bug: I had recently performed a cleanup of my project folder and deleted Dummy.chm, but unknown to me I suspect RoboHelp was still looking for it when opening the project, hence the permanent 'busy' doughnut and the crash when trying to do anything else, like opening a topic.