Comment 28 for bug 20765

(In reply to comment #22)
> I suggest the early comments be ignored and start fresh.

Original poster (mseele) laid out the users view of the bug very well.

Bug Description: Open new site in a Tab: Firefox freezes for 3-10+ seconds _exactly_ after the tab/window gets opened, the title name and grey background have been painted and the throbber starts rotating, but just before the first rendering is performed. The status on the bottom says: "Transferring data from <site>...".

Note: it usually happens when a new tab gets opened, but I have been able to reproduce the problem on new windows (right click, open link in new window) and have been able to see it happen after part of a multi-frame page got loaded and a further frame needed to be rendered. As the hang in the latter (frame rendering) case looks exactly like the Tab freeze I assume it is the same bug.

No other parts of the system are affected (e.g. no undue cpu load, no memory problem, other applications work fine... everything else is perfectly normal).
It happens under heavy and no load, with or without strong network traffic, with and without other programs running.

It is an intermittent problem: the only thing I notice is that when it happens: it is repeatable for a while (hours or the next one or two days) before it goes away. Also when I use the IE browser on the same sites, this does not happen! It also happens with Galleon under Linux but I have not tested that as intensively and no longer have that installed.

Bug happens on 3 different machines:
1) WinXP-sp1 (and sp2) Laptop PM 1,6 GHz, 1 GBytes
2) WinXP-sp2 P 2,8Ghz, 1.25 GBytes
3) Linux (Debian Sarge), P 1GHz, 256 MBytes

On any complex site URLs. Try: www.yahoo.com, gameguru.box.sk or gamespot.com

Happens with Firefox 1.0, 1.0.5, 1.0.6, 1.0.7, 1.5 RC1-RC2 and 1.5 final
Example Build: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8) Gecko/20051111 Firefox/1.5

_Ruled_out_ (see other comments): hyperthreading (#277547), version dependancy (see browser list above), OS dependency (see OS list above), processor dependency (except that all my processors are Intel), load dependency (happens under high and low load), low memory issues (stilL have 700-800 Megabytes of RAM left), DNS problems (did multiple tests on that), proxy problems (with or without proxies), network congestion timeout (different networks at different times using different connections with high throughputs and response times), font problem, history problem (cleared history), animated images (happens on sites with just text), extensions and plugins (clean install).

Example for freeze that rules out DNS timeout: One tab on slashdot, another on "http://www.sortasoft.com/index.php". I middle-click on "Other Games" to get this page in a new tab: http://www.sortasoft.com/othergames.php and my Firefox froze for 4 seconds.

Things that aggravate the problem: complex page builds make this more likely, network congestion or low bandwidth makes it more likely to happen.

Things that help: restart firefox (problem often reappears quickly though)

Suspected dupes of this bug: 248345 (has some good comments), 266627

Final words: all tests mentioned above have been tested against IE, which works flawlessly (in multiple windows instead of tabs of course). Obviously this bug only applies to a subset of users.
It would interest me what sort of connectivity the others who have this problem have... I have a German 2 MBit ADSL line (2000 down / 192 up) with path interleaving which slows down ping times by about 60ms.