It's better not to use external image hosters, rather attach them directly like I just did. ImageShack in particular is known to delete files after a while.
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I believe this is a side effect of a well-known issue:
Open Issues > "(146) Application needs to support 120 DPI throughout". As suggested in the Wiki, revert to the standard "Smaller - 100%" text size to fix that. There's no other known solution to this problem.
We have a habit of updating the Wiki as soon as new information is discovered if an issue affects many customers. If there were something we'd let the community know.