hidden share Folder Permission can't access

hi guys,

i got a strange things,i shared a folder with the name UDA$ in server 2008 R2,but in client, domain users can't access this folder in this way:\\dc01\UDA$,It showed no permission to access,but i used ip like this way\\IP\UDA$,the folder can be access ,every thing is ok.

also,i changed UDA$ to UDA，use this way \\dc01\uda, the Folder can access,every thing is ok,too

i can't understand that,any guys know about that,please give me some advices,Appreciate your help!

Merry Christmas!!