I only recently started using avast and have registered it but get this error message:- 
Information about current update:
Last encountered error: The license key for this product is temporarily disabled.
I haven’t seen anything like this temporarily disabled and haven’t heard of this in the forums to date, so it is a little strange.
However you have a full 60 days unrestricted use using the demo key, so you have a little time to have this temporary disablement resolved.
Check your system date, especially the year, and make sure it is correct. Although I don’t see this being the cause/problem (if it were wrong) or returning a temporary disablement error, but a full blown error message, like invalid license or license expired, etc.
If after a time this isn’t resolved you could register again using a different email address and you should get a new registration key.
Were you using the trial version and then, after some time, start to use the Home version?
If not, and you’re always using the Home version, register it again. Maybe the robot that generate the keys was corrupt ??? :-[
I am having the same problem as diskordian had.
There was something wrong with my system’s BIOS and it changed the date back to jan 1 2002. The problem is fixed and I changed the date back to the correct one, but I am still getting the error message “The license key for this product is temporarily disabled.” when I try to update the virus definitions.
I’m using Avast Home 4.6 with a registration key that expires in August 2006
Here is a log if it’s of any use.
01.10.2005 09:56:00 general: Started: 01.10.2005, 09:56:00
01.10.2005 09:56:00 general: Running setup_av_pro-2b3 (691)
01.10.2005 09:56:00 system: Operating system: WindowsXP ver 5.1, build 2600, sp 0.0
01.10.2005 09:56:00 system: Computer WinName: X
01.10.2005 09:56:00 system: Windows Net User: X\Driber
01.10.2005 09:56:00 general: Cmdline: /downloadpkgs /noreboot /updatevps /silent /progress
01.10.2005 09:56:00 general: DldSrc set to inet
01.10.2005 09:56:00 general: Operation set to INST_OP_UPDATE_GET_PACKAGES
01.10.2005 09:56:00 general: Old version: 2b3 (691)
01.10.2005 09:56:00 general: SGW32P::CheckIfInstalled set m_bAlreadyInstalled to 1
01.10.2005 09:56:00 system: Computer DnsName: x
01.10.2005 09:56:00 system: Computer Ip Addr:
01.10.2005 09:56:00 internet: SYNCER: Type: use IE settings
01.10.2005 09:56:00 internet: SYNCER: Auth: another authentication, use WinInet
01.10.2005 09:56:00 package: Part prg_av_pro-2b3 is installed
01.10.2005 09:56:00 package: Part vps-53902 is installed
01.10.2005 09:56:00 package: Part news-42 is installed
01.10.2005 09:56:00 package: Part setup_av_pro-2b3 is installed
01.10.2005 09:56:00 general: Old version: 2b3 (691)
01.10.2005 09:56:00 file: SetExistingFilesBitmap: 699->127->127
01.10.2005 09:56:00 general: GUID: 188a4fef-cedb-42a2-aca4-b5be5a1f0c21
01.10.2005 09:56:00 general: Server definition(s) loaded for ‘main’: 26 (maintenance:0)
01.10.2005 09:56:00 general: SelectCurrent: selected server ‘Download1 AVAST server’ from ‘main’
01.10.2005 09:56:00 general: Entered SetupProcessPro::Do( INST_OP_UPDATE_GET_PACKAGES )
01.10.2005 09:56:00 general: Entered SetupProcessWin32Avast::Do( INST_OP_UPDATE_GET_PACKAGES )
01.10.2005 09:56:00 general: Entered SetupProcessWin32::Do( INST_OP_UPDATE_GET_PACKAGES )
01.10.2005 09:56:00 general: Entered SetupProcess::Do( INST_OP_UPDATE_GET_PACKAGES )
01.10.2005 09:56:00 general: progress thread start
01.10.2005 09:56:00 general: progress start - 1
01.10.2005 09:56:01 general: progress start - 2
01.10.2005 09:56:01 general: Server definition(s) loaded for ‘main’: 26 (maintenance:0)
01.10.2005 09:56:01 general: SelectCurrent: selected server ‘Download13 AVAST server’ from ‘main’
01.10.2005 09:56:01 general: Invalid value (1)
01.10.2005 09:56:01 general: Invalid licence: 0x2000001D
01.10.2005 09:56:01 general: progress end - 1
01.10.2005 09:56:01 general: Err:The license key for this product is temporarily disabled.
The solution will be uninstalling / boot / installing again / boot. This seems to be the behavior of the antipiracy feature of avast.
You can use the same Registration Key 
I’ll try that
forgive my probably daft question 
but how can you pirate software that is free?
The Professional version of avast is not free…
Only the Home version is.