Firefox gets slower & slower in Ubuntu 12.04

[Martin J. Marsh]

For some reason Process Manager in system Monitor shows that PulseAudio is showing an abnormally high level of usage, but I'm not using any audio for most of the time when browsing.

OK, still using Ubuntu 12.04, when newer versions are available (though might be too much for an old Pentium 4), but there has to be some reason why, using the same T-Mobile mobile dongle as before and going to more or less the same pages, my connection has just recently got very slow indeed. Do I need an anti-spyware and anti-virus clean-out I wonder, but I have been told by Ubuntu enthusiasts that Unix, Debian or Linux based systems are not so vulnerable.

Since installing this 12.04 version of Ubuntu after using 10.04, I've been wondering if it was a "dumbed-down" version from the start, as the system does not seem to have the same capabilities as previously, does not recognize my mobile Broadband connection (via Sakis3g) even when it is active and working for web pages and downloads. Software center cannot be properly used because the web connection is not recognized. The "right-click" on my mouse seems to offer less options than previously. Web pages are getting slower and slower to load.

System Description: Ubuntu 12.04.5 LTS Release 12.04