Comment 19 for bug 136632

I agree : lyx 1.5.1 on Gutsy is too slow with my current document : I have to wait for 1 second between typing each key :(

To improve Lyx performance, just update your lyx version to 1.5.3

1/ you don't fear to upgrade to Hardy Heron :p

2/ you want to stick on Gusty Gibbon, so install the backport

a/ update your /etc/apt/sources.list to enable backports
see https://help.ubuntu.com/community/UbuntuBackports#head-64200fc3461be5e8062b5df39c80c115cb067ec9

b/ update your lyx version
apt-get update ; apt-get install lyx

c/ remove or comment the backport repository in your /etc/apt/sources.list
in order to prevent unintentionnal system wreckage :p

Voila !

Nop