It sounds like there may be a corrupted file.
Try downloading Export content again and unzip it locally then FTP the files into place.

Everything except export_content.php will go in :
/administrator/components/com_export_content/...

Also if you can try compiling for Joomla 1.5+ and tell me what happens.

Done. I manually updated all sites with the newly downloaded files.

Compiling all 6 sections for 1.0 brings the same error as above. For 1.5 I get the following:
Error deleting ../administrator/components/com_export_content/zip/ import_content_data.zipDeleted ../administrator/components/com_export_content/zip/ import_content_data.xml

Only doing 3 at a time still works for both.

The real problem is the insertion in the target site.

Results are still the same when inserting on the 1.015 site - goes straight to a blank page.

On the 1.5 site the insertion works like a charm.

oops forgot to add...

I also am getting a blankish page as soon as I click on insert by category. The other ones don't break until I click save on the summary page.

I have tested on 1.0.15 and I can not reproduce the error.

Have you tried a re-install of Export Content?

Although you have checked permissions I still think that that is the problem.
You could try changing permissions site wide to test if the issue is coming from elsewhere like /includes

Or if you are having success with moving a few sections at a time maybe that's what you will have to do.

If you find the solution please post back as it may help anyone else that runs into it.

I'll keep trying I guess.

I can't move a few sections at a time, or I'd already have done that. The compilation works with a few at a time, but the insertion breaks with just one.

If I find something I'll post back.

When trying to insert if there is already a section/category with the same name you will get an error.

Also when compiling Export content will attempt to build a list of required images so you might want to check permisions on the /images.. directory

Have you made any changes to the standard database?