If a newsgroup has a long thread (several hundred articles), expanding it takes several seconds and UI is completely frozen whih those seconds last. Reproducible: 100% To reproduce: 1) Post 1000 messages with subject "AAA" to a newsgroup and set to to be sorted by thread. 2) Try expanding the thread Expected: Expension is fast, UI does not freeze. Actual: Takes several seconds, UI is frozen while it lasts. Mozilla versions: probably had this for over a year, up to BuildID 2002072504 (trunk). P.S. Collapsing is fast, expanding it back is slow again. I have a ng with about 1500 messages with several large (up to 630 messages) threads. "Expand all" after "Collapse all" makes Mozilla freeze for over 20 seconds on PIII-450. P.P.S. I suspect this might be already reported, but couldn't find it. Sorry if it's a dup.

taking - I wonder if we need to batch the inserts into the tree.

WFM This problem should be gone with bug 90452 and others fixed. Please reopen if you see this using a current version.