Whenever I close K-Meleon, I have to kill the process through task manager before I can launch it again.

Maybe tell which version makes fault: else i assume 0.9 official.
That 0.9 only does that "hanging" only
after being damaged or wrong alterations by user.

As to my experiance this hanging is typical of script related faults.
Especially in test versions or after tracing Java Script faults with k-m that have been altered to do that kind of job.

Problem: k-m also consists off scripts. Did You alter anything e. g. in skin,
macros or menues recently? Means something might be damaged by accident
or alterered by user input.

go to java console and check for script fault. maybe You get a clou from there.
If You do not find a reason via console, did not change anything Yourself
or do not use a test version?

Else something might be damaged (they are only machines and can be damaged).
Do the normal things, create a new profile test whether that works ...
ultimate ratio when all fails new install at new location ... like K-MeleonNew.

Javascript Console is located in the menus at:
(Tools > Advanced Preferences > Javascript Console)

Brian

Sorry, yeah it's version 0.9, although I have this issue with K-Ninja and K-MeleonCCF 0.4Final as well.

There's nothing at all in javascript console.

I did edit Macros and Menus to add Clusty as a search engine.

This is how macros looks, I didn't change anything else in there

Engines{
macros(Clusty)
macros(Google)
macros(Yahoo)
macros(Wikipedia)
macros(Dictionaries)
}

# ----ENGINES----
Clusty{
&OldSearch; $search = "Clusty";
$eng = "http://clusty.com/search?query=";;
&SetSearch;
}

Nothing in console is a good sign, but does not help us futher.
macro also looks good to me.

I assume; You will have to look if a new install helps
(rememeber to use differnt name and location for it)
- sorry that i can not help any better.

p. s. You say trouble with several versions - when did it start what did You alter?
New software ? Maybe it reminds another user of something that is of help.