I've not heard experienced or heard of trouble with this particular
operation, but I'm familiar with the Trusted site  bit (when you're trying to
avoid endless login prompts). If you're using IE 6, you want to add the SP
site to your Trusted Sites zone; if IE 7 or above, then add it to Local
Sites.

The error  you're describing doesn't seem to be a versioning problem. Have
you checked the application logs (via Event Viewer) and the SP logs in the
12 hive?

If you are using WSS 3.0 or MOSS 2007 and if you are using Excel 2007 I
learned that you need to format your list  as a Table from the Styles
group on the Home tab of the Ribbon with a Table Name which can then be
imported.

There were no entries in any of the 12 hive logs nor anything in the Event logs
on the portal. My local App log has:
Faulting application excel.exe, version  12.0.6331.5000, stamp 48fa2869, faulting
module kernel32.dll, version 5.1.2600.5512, stamp 4802a12c, debug? 0, fault
address 0x00012aeb.

Haven't been able to find  any solutions.

Tried that but still no luck..............

I found a work around:

Using Excel 2007, format the data as a table, then under the Design tab on the
ribbon, use the Export (External Table Data) to PUSH it from Excel to MOSS,
instead of PULLING.

It doesn't solve the original problem but it works.