RMAN Backup To Shared Network Drive?

I scheduled a RMAN backup job to take FULL database backup to a shared network drive.

RMAN Script used:

RMAN> run
2> {
3> allocate channel ch1 device type disk format '\\BACKUP1635\X$\ARC%U';
4> backup database plus archivelog;
5> release channel ch1;
6> }

Environment: Windows server 2003 OS and Oracle 10.2.0.4.0

Iam facing below error.

RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of backup command on ch1 channel at 02/20/2011 18:19:46
ORA-19504: failed to create file "\\BACKUP1635\X$\ARC1BM55JL8_1_1"
ORA-27040: file create error, unable to create file
OSD-04002: unable to open file
O/S-Error: (OS 5) Access is denied.

I checked shared network drive and found READ/WRITE access for me. I am able to take RMAN backup in local system without any issue.