samba - May 2004 - cannot write to but read from shares with mount.cifs

Hi list,

we have a file server on which Win2k3 (EE) is installed. I can mount my 
home drive from a linux machine (gentoo with samba-3.0.2a-r2 installed) 
with my windows account data and mount.cifs. Then I can read files or 
navigate through the dirs. But if I try to write a file I get "permission 
denied". If I do the same thing as Administrator no error occurs.

Well, one could say that my windows account doesn't have enough 
permissions to write to certain shares but it works if I try to map my 
home drive from a windows box.

Are there any policies or adjustments which I have to make to get this 
working? What am I doing wrong?

TIA

Timo