When trying to insert tab seperated data in the spread sheet, I am able to enter
the URL of the source document in the local filesystem.
The Text Import window appears, the fields are correctly recognized and
displayed in the scrollbox in the Fields section. 
In the Separator options section: Seperated by Tab is set.
If I now press OK, I come back in the External Data window, with the URL filled
in, but the OK button is grey, and I can only press Cancel or Help.

This is the same in OOo 1.0.2 

In MS-Excel, I get the same dialog, but instead of using insert/external data, I
must use file/open, whereafter the data is correctly displayed in Excel. When I
try this in OOo spreadsheet, I end up with the file being openend in Writer.