a2uploader won't recognize the phone

Some of you have encountered a problem when you connect the phone to computer, the a2uploader still waits for it. Now, here are 2 possible causes. One of which can be solved in a flash, while other demands a bit of cleaning :P

To make this as easy as possible: For a2uploader to connect to your phone's FS you need to have SEMC Flash Device driver installed. There are several ways to get that driver. My recommendation is to download and install Sony Ericsson Update Service.
After installation, use it at least once (its very easy to use, follow the on-screen instructions and READ, backup your phone stuff!). It will install the driver in the process of updating.
Updating your phone's firmware will fix some crashes that may have been occurring, it increases your phone's performance, and in some cases adds new features. It also updates drivers for camera and acoustics, therefore improving the quality of both.
If the Update Service has successfully updated your phone you can be 100% sure that a2uploader will work now.
If the Update Service didn't work, there is no chance the a2uploader would.
Clean your phone! Clean the metal connector on your phone, there might be problem with metal contacts between the phone and the cable, preventing the connection. If it still doesn't work contact the Sony Ericsson Support. Not because of a2uploader (come on, don't be stupid), but because of the Update Service.

As you can see, here I'm using the official software, SEUS, for testing if a2uploader will work. Just because the official software has support. If SEUS won't work there is no chance a2uploader would.