Following comes from Senior Support Engineer Deepak Mittal.
You may notice junk characters in the Team Build 2010 log while copy operation on the dlls.
Error messages were something like this:
Overwrite D:\Builds\Microsoft.ABC.XYZ.dll (Yes/No/All)? ? ╖ µ═∩ƒ≡Ω ≥dΣ ⌠±0d. ÿ√ pi. ░j.pj. ⌠± ⌠± (IΣ ░∩
pi. b. ÿ√ ¡aP√- °¡a(²- HΣ 
% 1 b y t e s t o t a l d i s k s p a c e .
< % 1 b y t e s i n b a d s e c t o r s .
D % 1 b y t e s i n % 2 h i d d e n f i l e s .
8 % 1 b y t e s i n % 2 f o l d e r s .
While working on a case recently, we found junk characters in the build log file. TFS migrated from 2005 to 2010 and using upgradetemplate.xaml.
Apart from junk characters, there were misleading error messages like check the disk, bad sectors which were pointing us to issues with hard disk which was not the case actually. We found that these all happened while performing the copy operation on the dlls from release folder to another folder in the drop location. Copy operation was performed in the task in TFSBuild.proj file.
We found that the issue was happening as the copy and xcopy commands were prompting for overwriting the files in the build log. To resolve this issue, we used copy command with /y flag which suppress the prompt for overwriting the dll.