[Sage] problems importing Sage's OPML into Thunderbird

[F.D.]

Hello guys,

I just imported my feed list from Sage into Thunderbird 1.5 (via OPML 
ex- and import).

Unfortunately, this created a huge mess in TB; instead of retaining the 
category folders I'd created in Sage, each feed suddenly had its own folder!

This is what it looks like in Sage:
* Gaming
   - Eurogamer
   - GameSpot
   - ...
* Web News
   - Slashdot
   - ...
* ...

And here's how Thunderbird understood it:
* Eurogamer
   - Eurogamer
* GameSpot
   - GameSpot
* Slashdot
   - Slashdot
* ...

I realize this is probably Thunderbird's fault - still, does anyone 
happen to know how to fix this problem? Maybe by creating an XSLT 
conversion from Sage's OPML to Thunderbird's FEEDS.RDF (located in » 
*...\profiles\[user]\Mail\News & Blogs\* «)?

By the way: I do not intend to abandon Sage, but I need to use 
Thunderbird for feeds on the laptop.


Regards

Frederik