WMWare does not really work out of the box on Ubuntu.
There is an issue concerning the ACPI, which makes the guest machine so slow that it is barely usable.
If you do on your terminal :
$ cat /sys/module/processor/parameters/max_cstate
You will probably get a value bigger than 1. In my case, it was 8 (default in Ubuntu, I guess). This value is related to the number of level that the processor takes to save energy (reducing its performance and power consumption when idle).
For a try, fix it to a smaller value and check how VMWare is going :
$ sudo -s $ echo 3 > /sys/module/processor/parameters/max_cstate
I think 3 is a good compromise. At least it is working very well on my machine, no slow down at all. If you still have the issue, reduce it to 2 or even 1. The side effect is that your laptop will be a little bit more power hungry, but so little that you probably won’t see any difference.
If you stop here, you will loose the change at the next startup. To have it set on boot, edit the /etc/init.d/acpid file.
Add the line at the end of the function named load_modules() :
echo 3 > /sys/module/processor/parameters/max_cstate
I found out the solution thanks to this article. Go there for more info or alternative solutions (including for different systems).
I hope this will be helpful.