1) Try to increase the virtual video memory to 1024mb (or set to max, can't remember the maximum allowed size) and lower the virtual RAM memory accordingly.
2) Some users have had similar problems:
I had same problem running Min13 64 on a windows xp x64. The problem
was related to chipset and audio controller used during virtual
machine creation. Now using PIIX3 and ICH AC97 and after reinstalling
Mint, both video and audio works smoothly
I had the same problem with xfce version. It turned out to be a simple mistake - I've chosen Ubuntu as OS option while creating VirtualBox machine. Once I recreated it with Ubuntu64 and reinstalled Mint, everything became fast and nice (2G on 1 CPU). No need to install additions either as they appear to be included with the distro.
3) There's a tutorial to make firefox faster: http://community.linuxmint.com/tutorial/view/338
Before making any changes, please make a backup of .mozilla/firefox/--------.default/prefs.js for your own safety. prefs.js is a file that stores all of your history and bookmarks from Firefox.
First open Firefox.
Type "about:config" (without quotes) in the Firefox address bar and then click "Enter". This command opens a configuration page that allows the user to change advanced system settings in Firefox.
Speed up page loading/rendering time in Firefox. Right-click anywhere in the "about:config" window, click on "New" and then select "String". Name the string "nglayout.initialpaint.delay" (without quotes). Enter a value of "0" and then click "OK". This tweak decreases the amount of time Firefox waits to render a page from 250 milliseconds to zero. Make the same process and name the string "content.notify.interval" and enter a value of "0".
Force Firefox to release reserved system RAM when the browser is minimized. Right-click anywhere in the "about:config" window, click on "New" and then select "Boolean". Name the entry "config.trim_on_minimize" (without quotes). Change the value to "True" and then click "OK". This setting forces Firefox to only reserve about 10 MB of system memory while minimized.
Normally Firefox only sends one or two tunnels to the website. However, the more tunnels you use the faster you go. To change this, type in filter bar "network.http.pipelining.maxrequests" and change the value to "150".
Attention: The more tunnels you use, the more bandwidth you use, meaning you could use as tunnels as you want but that would probably kill the sites bandwidth if everyone did that. 150 is a very good value.
Type "network.http.pipelining" in filter bar, and set it to "True" by double clicking it.
Type "network.http.proxy.pipelining" in filter bar, and set it to "True" by double clicking it.
4) Also try to backup your firefox settings and reset your Firefox to default:
In short, head to
about:support (or from the menu Help > Troubleshooting Information) and hit the reset button. You will have to reinstall your data and extensions.