Your comments

Thanks, I'll try to find out what's going on.
I'll try to setup a test system with Windows 7 and IIS WebDAV. Do you have a link to installation instructions you followed? Just to make sure I'm using the same configuration.
Are you sure that this only happens with spaces in the folder name?

I've recently discovered another error that results in a crash when the WebDAV server doesn't send a ContentLength header. This error happens as soon as you try to download a file.
Just tap on the editor once with two fingers.

This is currently explained in the Gettings Started file, but not yet in the manual.
Unfortunately, I don't have such a GMX Mediacent or 1&1 Smartdrive account. Would it be possible to send me login details so I can try to reproduce the issue?

If yes, please send the information to support@textasticapp.com.
The tabs in iOS 5 beta 3 are limited to a number of 8 so that they are still touchable. Also, in Safari, most of the time you don't have the on-screen keyboard visible all the time like in Textastic.
You can send the file to support@textasticapp.com
Yup, thanks for letting me know.

I already submitted an update to Apple which was supposed to fix this issue, but it also fixes some other odd behaviour on iOS 5. The update should be available any day now.