Assuming you have not accidentally opened an older data file, have you tried reindexing the file? CMD-OPT-B (be sure to have backups before doing this).
Alternatively, you can try saving a copy of the file via the File > Save a Copy menu, which reads the original data file and recreates it. This sometimes cleans up anomalies in the file.
Things sometimes seem to disappearin Quicken 2007, and re-indexing -- as mentioned above -- magically restores the transactions which seemed to be missing.
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