Error rendering macro 'viewxls' : PermGen space - Powered by Atlassian Confluence 5.6.5

Hello there,

We're using Confluence 5.6.5 and the 'viewxls' macro suddenly stopped working on multiple pages for our users. Some of the pages haven't been touched for months and the attachments aren't particularly large, attaching some screenshots.

Not sure if there is any more info you could use to take a look at this but if so please let me know and I'll try to find out.

Thanks,
Kamila