Error couldn't install on USB storage or SD card

"Error couldn't install on USB storage or SD card" Is anyone else having this problem? Does anyone know how to solve this problem? If so, please enlighten me on how to resolve this issue.
This problem started about a month ago from out of no where, when previously I was able to load and install new app to SD card without too much fuss, or even update already installed app on SD card. Now anything that is on SD card has to be moved to phone before it can be updated and then move back to SD card. And new app that installs directly to SD card can't be install at all. Unless it is installed on phone first and then moved to SD card if and only if the app allows it.
I don't know if I've erased any function by mistake (is that even possible?) Or has some update caused this without me knowing?
Anyway any advice on how to resolve this would be greatly appreciated since we all know that the Desire doesn't carry a lot of memory on the phone itself. (I'm not rooted by the way)
Thanks in advance.

Still no reply in this forum from any expert or anyone with the same problem. I've have come to live with it by installing apps that i would use often and uninstalling old or non-useful apps so as to have enough memory on the phone. Anyway will probably be getting a new phone with more memory soon.

I have finally cured this problem, unfortunately the only way to do it is to do a full factory reset, no biggy though just back up everything you want saving and reinstall once reset is done.
hope this helps folks

Mick

Connect your phone to your PC as a mass storage device or connect sd card with a cardreader

Backup important data

Find the folder named “.android_secure”

Inside it, delete the file called “smdl2tmp1.asec”

Disconnect your phone

Install the App you were trying to install