I can't be 100% sure, but your problem sounds similar to one discussed in this thread:
http://kmeleonbrowser.org/forum/read.php?f=1&i=2653&t=2653
Relevant bits, edited for clarity:
"There is a known bug where if you save more than one username/password you will get the error that you encountered. You can either try editing this file* using a text editor to remove the offending username/password... or delete the file entirely and it will recreate itself."
*the file's name is a random number with an extension of "s" (eg. "1234567.s"). It is found under.... C:\Program Files\K-Meleon\Profiles\default\xxxxxxxx.slt\
How to edit the .s file (it's easy!):
1. Close K-meleon.
2. Open the file in your favorite text editor (preferably _not_ Notepad, which screws up the formatting on my computer. WordPad works great for me.)
3. Search the file for url's that appear more than once (in this case, multiple entries for www.dslreports.com).
4. Delete the offending entries completely (url, login and password).5. Save and exit the file, open K-meleon.
6. Visit the previously offending site. Do a little dance when K-meleon doesn't crash.
7. Remeber to never save info to Password Manager more than once per site.
Hopefully this is what's causing your trouble. I don't know how necessary the step by step instructions were, but maybe someone else with the same problem and no computer savvy will read this and find it helpful.
Good luck!