firefox crashes frequently

Please submit the crashes to Mozilla and attach the crash ID here

Firefox doesn't seem to crash anymore, if it crashes I'll post here the crash ID

It crashed again. I have submitted the crash to mozilla. Here is the debug info it showed me:
Add-ons: {a0d7ccb3-214d-498b-b4aa-0e8fda9a7bf7}:20100908,{cd617375-6743-4ee8-bac4-fbf10f35729e}:2.8.1,{888d99e7-e8b5-46a3-851e-1ec45da1e644}:4.0.1,<email address hidden>:1.0.3,{cd617372-6743-4ee4-bac4-fbf60f35719e}:2.0,<email address hidden>:2.4.2,<email address hidden>:0.78.2,{ef4e370e-d9f0-4e00-b93e-a4f274cfdd5a}:1.4.1,<email address hidden>:1.0.1,<email address hidden>:4.0.1A,{7BDB48D1-CD94-4B99-A5A4-E418B9EE6532}:1.1.1,<email address hidden>:0.9.2,<email address hidden>:1.2.3
BuildID: 20101122200949
CrashTime: 1292685407
EMCheckCompatibility: true
Email: <email address hidden>
FramePoisonBase: 00000000f0dea000
FramePoisonSize: 4096
InstallTime: 1290530326
ProductName: Firefox
StartupTime: 1292653236
Theme: LavaFox_V1
Throttleable: 1
URL: https://secure.wikimedia.org/wikipedia/en/wiki/Special:Search?search=A-GPS&sourceid=Mozilla-search
Vendor: Mozilla
Version: 4.0b7

Crashed again.

Add-ons: {a0d7ccb3-214d-498b-b4aa-0e8fda9a7bf7}:20100908,{cd617375-6743-4ee8-bac4-fbf10f35729e}:2.8.1,{888d99e7-e8b5-46a3-851e-1ec45da1e644}:4.0.1,<email address hidden>:1.0.3,{cd617372-6743-4ee4-bac4-fbf60f35719e}:2.0,<email address hidden>:2.4.2,<email address hidden>:0.78.2,{ef4e370e-d9f0-4e00-b93e-a4f274cfdd5a}:1.4.1,<email address hidden>:1.0.1,<email address hidden>:4.0.1A,{7BDB48D1-CD94-4B99-A5A4-E418B9EE6532}:1.1.1,<email address hidden>:0.9.2,<email address hidden>:1.2.3
BuildID: 20101122200949
CrashTime: 1292688574
EMCheckCompatibility: true
Email: <email address hidden>
FramePoisonBase: 00000000f0dea000
FramePoisonSize: 4096
InstallTime: 1290530326
ProductName: Firefox
SecondsSinceLastCrash: 3167
StartupTime: 1292685547
Theme: LavaFox_V1
Throttleable: 1
URL: http://www.youtube.com/watch?v=fKqxB5w4ukg&list=QL&playnext=14
Vendor: Mozilla
Version: 4.0b7

I need to the actual crash ID for the report to be of any use. You can get this from about:crashes

bp-584c6459-e8c4-4e72-aecf-c0bc12101218 for the first crash
bp-9243e3a4-b664-40fe-ae4d-629f62101218 for the second one

Thanks. Those traces look like purely an upstream problem rather than being something specific to Ubuntu (it also occurs on Mac OS X), so I'll close this report here. We don't handle Firefox crash reports in Launchpad any more, unless they're a distro problem.