I'm using XP SP3 with 0.48 Inkscape. I had the same issue with 0.47 Inkscape as well. It's why I upgraded. Here's more detail.

First I created objects using the bezier tool and the circle tools. I converted these objects to paths and combined them. I coped this new object then selected the pencil tool with the smoothing at 50 and the shape From Clipboard (my previously mentioned object)

I then wrote some text.

Then drew a long wavy line, selected it, turned it into a path (Object To Path) and then selected both the wavy line and the text and clicked on Text >> Put On Path. Which it did!

Then I needed to move the text into position. So I clicked Alt and the right arrow to move it. It always starts well but then slows right down and crashes.

I've tried only moving the text a small amount and then doing something else before coming back and starting again but that doesn't work.

When it crashes the program it comes up with two error messages. The first:

I've done a little screen video to show you exactly what is happening. View here >> http://www.youtube.com/watch?v=CLrcSvYKwkA

The first error message is: gLib-ERROR**: gem.c:136: failed to access 56392 bytes aborting...

The second error message is:

Runtime error!

Program: C:Program Files\Inkscape\inkscape.exe

The application has requested the Runtime to terminate in an unusual way. Please contact the applicants support team for more information.

End quote...

I've put this on launchpad as well. I can't seem to find anything that matches this anywhere and while I'm ok with using computer stuff I'm definitely amateur status so I hope I have this in the right place! Thanks for your time.

I think you are confusing inkscape by giving it a path to put text on that is the product of another path effect called pattern on path which is automatically applied when you do 'from clipboard'.

Possible solution: when you have your swirly path just right, do object to path (Path menu) this removes the path effect , and then shift select your text and do text on path. This puts the text on a path. Now you can kern it without problems. However you have lost the editability of the path. You could try putting the text on a copy of the path, and then giving the path no style to make it invisible.