Have you come across this notification when you're trying to update your apps from the Android Market?
unknown error -18. APPNAME unsuccessful
Well it's been happening to me since I updated my software to froyo 2.2. on my HTC Aria. After going through some forums, I've found the solution to the problem which has worked well for me.
Here are some step by step instructions to fix this problem:-
Step 1:-
Connect phone to the pc using the USB cable and change the connection type to "Disk Drive" (Mount as disk drive)
Step 2:-
Open the phone's directory on your computer.
Step 3:-
Open the folder ".android_secure"Step 4:-
Delete the file "smdl2tmp1.asec".
Step 5:-
Unmount your phone and wait for the apps to reload, it usually takes only a few mins and you'll find that you will be able to update your apps again.
Thanks for reading and hope it helps :)