following example using roundup-admin modifies the
"category" field in the issues specified to contain the
literal string "container" instead of the number of the
actual item of the "category" roundup class. The
problem does not occur with the *dbm backends.
roundup-admin -u schlatterbeck -i
/tttech/org/software/roundup/tttech set
issue5544,issue5543,issue5546,issue5538,issue5537,issue5536,issue4203
category=container

If specifying the number of the "container" item in the
roundup class category (56 in our db) the roundup-admin
command works as expected.

Maybe the same cause:
in the programming interface using a query 
status = ['open','feedback','analyzed','testing']
filterspec = {'status' : status}
for issue_id in db.issue.filter (None, filterspec,
sort=('-','priority')) :
[...]
will not yield any results (nothing is matched by the
filter).
If I use 
status = \
    [db.status.lookup (i) for i in
['open','feedback','analyzed','testing']]
the expected issues are returned by the query. Again
this works ok with the *dbm backends but does not with
the sqlite backend.