Version:           4.8 (using KDE 4.8.0) 
OS:                Linux

Any time a mail with a long body (>1500lines) is being dealt with, Composer becomes very slow for both opening and navigating within the text. While doing so, Kontact thrashes the CPU up to 100%.

Reproducible: Always

Steps to Reproduce:
1) Select a mail with a long body (tried with > 1500lines)
2) Choose "Reply" or "Forward inline"

Actual Results:  
The composer window opens and remains inactive (grey) for several seconds - delays up to 10s have been observed. When open, navigating within the message body is also very slow - e.g. jumping from the end to the top (Ctrl-Home) can take 2-3s, again while thrashing the CPU. This makes dealing with long mails very cumbersome.

Expected Results:  
Composer should pop up quickly and be responsive within a short time. Navigating within the message text should be smooth and not dependent on text length.

- Set-up: Kubuntu 11.10 with either the original 4.7.4 packages or the Kubuntu-ppa 4.8.0 packages, IMAP account, NFS4 home directories, akonadi working with a central MySQL server.
- The bad performance was seen with both Nepomuk disabled and enabled.
- When using "Forward as attachment", Composer appears more or less instantly and is much more responsive - the slow down seems directly related to the length of the message body.