I know... already feel guilty about emergency dentist appointment and taking the rest of the day off ;)
Steve's right, a support ticket is the best way to get 'attention' to a problem, the forums here are great place, but can't guarantee anything in terms of response time. Consider these tips (probably once you did already)... since I don't know the Sitefinity version number nor the troubleshooting steps you took
Try a different theme & template for the page.
Usually if backend page editing breaks, its because something in the theme or template is breaking/missing. Go to design >> page templates
edit the template the product list widget is on and change the theme to 'Basic
'. If you go back to your page editor and things still don't work - on the page edit screen click layout
, bottom right change template
and change it to a default one.
Drop a product list widget on a newly created default template/basic theme page.
Create a new page, with a Sitefinity default template and the basic theme and drop the product list widget on it. If it still doesn't work, the problem is definitely in the product list widget or the the widget template you created for it.
Try the product list widget with the default widget template.
If you have altered the default widget template, or using an external overriding template ~/ctrlpresentation/guid-bla-di-bla.ascx try it with the default Sitefinity one.
If it works, the problem is in your template...
Drop a buy-now-widget on the test page.
The buy now widget uses the same code base to retrieve a single product, drop it and see if it works.
If it does, your underlying product catalog is ok. If not, then the problem lies in your product configuration.
Ok styling issues and custom design/coding issues are out of the way...
I'm pretty sure you've ran into the issue by now, because you seem to be able to browse to the '.../brokenpage/Action/Edit' page and the editor is showing up. The only thing running from that point onwards (drag-n-drop) is /Sitefinity/Services/Pages/ZoneEditorService.svc
Fiddler 404 & 500 verification.
Use Fiddler to verify that you don't run into any 404 or 500 errors when accessing the page.
If you don't know Fiddler, just download it here
and run it. While it's running, start up the website and browse to the Sitefinity Backend >> Pages >> Edit the page and (try to) drag-n-drop a widget. Now look at the Fiddler timeline again, if something shows up in red with a 404 (not found) or 50x (permission issue) you know where it's coming from.
Temporarily remove catalogconfig.config & ecommerce.config
In the /App_Data/Sitefinity/Configuration folder you'll probably find the file 'CatalogConfig.config'. Remove it, recycle app-pool and try Sitefinity again. This file contains customized settings you've altered from the 'out-of-the-box' setup, but since it also stores GUID's there might be a mismatch.
When you're back in Sitefinity, go to Ecommece >> Configuration
first and set the proper options (mainly tax items which are guid based)
If all else fails republish products...
Have you tried editing and saving the products again? Sure hope you don't have many but since you're guessing its db related and I'm guessing for a code related issue (template/page or widget template) if it's db related to the products you shouldn't be able to do this.
Known issues regarding ecommerce
There was a search related issue when you had a search index that included a product search it broke the product catalog but unless you have one on production and not one on development, that shouldn't be the issue.
Also Sitefinity introduced breaking changes with regards to retrieving images, so this might be the cause of your issues but the error just isn't displayed...
And finally, some .svc weren't included in the visualstudio project (being part of the solution) so they wouldn't get published. On v4.4.2117 & v4.4.2182 the /Sitefinity/Services/Catalog folder should contain 2 .svc files and the /Sitefinity/Services/Ecommerce/Catalog folder should contain 7 items. Where as in v4.3.2054 the /Sitefinity/Services/Ecommerce/Catalog folder contains 6 (ProductVariationsModuleService.svc is added in v4.4)