That may be a bug introduced when we pushed some code changes 
Thursday.  I'll get it fixed as soon as I can.
>/user/diggboss/submissions?count=100
Yeah, looking at the response, I can see the implicit time period was applied:
<stories timestamp="..." min_date="1216809840" total="29" offset="0" 
count="29">
Note the min_date in the header, which tells us only the last 30 
days' submissions were returned.  That's the implicit time period for 
many List Users calls, but not when a single user's submissions are 
requested, as documented here:
http://apidoc.digg.com/ListStories#Arguments
Thanks for the report.
We just pushed a fix for that problem.
Sorry it took a couple of days.  We've been very busy getting ready 
for the Democratic convention, where the API will play its part!