I think it's rather unlikely... but there could be a file that avast! is having problems with.
A few questions:
What are the settings of the scan? (i.e. is it quick/standard/thorough, is the "archives" checkbox checked?)
Where does the scan stop (i.e. what is the name of the folder)?
Please go to the program Settings and turn on the generation of the report file. In the configuration, mark all kinds of files to be included in the report (even "OK files", which will make the report quite huge).
Now, run the scan again... when the scan freezes, check the end of the report file - the last scanned file should be close to the end.