Out of memory errors usually are caused by one of the following:
1 - There are more feeds/items than can be stored in memory. The number of feeds you have and the number of items per feed in large part determines the amount of memory used by DoggCatcher. Try lowering the max items, especially if you have a large number set for the global preference for max items.
2 - A feed with a large feed thumbnail. Occasionally feed publishers will include a feed thumbnail that is larger than the amount of available memory for the application. DoggCatcher tries to protect against this, but it's not always possible.
This also varies a bit by device. The earlier Android devices made 16 MB available to each application. Newer devices made 24 MB available. I believe the Honeycomb tablets support even more.