Hi! This bug occours in lyx 1.3.0pre2 with both qt and xforms frontends.
Open the attached file and select the hole equation, then Edit -> Copy (or Control-C). Lyx freezes for a while and spends several seconds in maximun cpu usage. After this, it is enough to select the equation again (no need to copy) to reproduce this behavior. In a text with a lot of complex equations, selecting and copying can freeze lyx for several minutes. Joćo.
#LyX 1.3 created this file. For more info see http://www.lyx.org/ \lyxformat 221 \textclass article \language brazil \inputencoding auto \fontscheme default \graphics default \paperfontsize default \spacing single \papersize Default \paperpackage a4 \use_geometry 0 \use_amsmath 0 \use_natbib 0 \use_numerical_citations 0 \paperorientation portrait \secnumdepth 3 \tocdepth 3 \paragraph_separation indent \defskip medskip \quotes_language english \quotes_times 2 \papercolumns 1 \papersides 1 \paperpagestyle default \layout Standard \begin_inset Formula \begin{eqnarray} & \frac{r^{2}}{\sqrt{-g}}\left[\partial_{2}\left(\sqrt{-g}\, g^{22}\partial_{2}\right)\right]=\nonumber \\ & =\frac{r^{2}}{\sin^{d-3}\theta^{2}}\left[\frac{\partial}{\partial\theta^{1}}\left(\sin^{d-3}\theta^{1}\, g^{22}\frac{\partial}{\partial\theta^{1}}\right)\right]\nonumber \\ & =\frac{r^{2}}{r^{2}\sin^{d-3}\theta^{1}}\left[\frac{\partial}{\partial\theta^{1}}\left(\sin^{d-3}\theta^{1}\frac{\partial}{\partial\theta^{1}}\right)\right]\nonumber \\ & =\frac{1}{\sin^{d-3}\theta^{1}}\left[\frac{\partial}{\partial\theta^{1}}\left(\sin^{d-3}\theta^{1}\frac{\partial}{\partial\theta^{1}}\right)\right]\end{eqnarray} \end_inset \the_end
