OK, when you receive and error message, please try to get the full error message and post it not a partial message text, this will help us to identify the potential cause and offer a related solution.
I'm sorry I can't help you with the ICQ issue, I don't use ICQ.
Reference the splash screen problem, I guessing here (because I don't recognise the error message, possibly incomplete) but it could be:
First check out this avast! FAQ answer
http://www.avast.com/eng/other_questions.html#idt_1406. For avast! Pro users it is best to update the ODBC Drivers, Home users can switch to XML storage.
You can manually edit the avast4.ini file (using a text editor) and change database=odbc to database=xml, this is in the [Common] section.
Or you can try RejZor's AEC
avast! External Control program and change the database type to XML
You can also use the forum search function as this will probably have been discussed before.