I found out about a major flaw in the calendar plugin for blosxom. after my website was suspended again. I started to wonder if there could really be a problem, since that happened with my previous provider too so I called up Bluehost's support team and asked about the problem. First of all, I have to say thanks to their support: contrary to my previous provider, they had a Call Center, which made things much smoother. Additionally, they were able to provide accurate information about the name of the process, the time, the amount of CPU usage, etc.
Thanks to those details and after a quick search in Google, I found an interesting page, where the problem was mentioned. Basically, if you input a bad month in the URL, the plugin will get into an infinite loop, which may use up all resources on the server.
The fix proposed in the page is quite simple: just run a test on the month, and if it's greater than 12 or lower than 1, just force its value to 12 (for example). Assuming there may be other problems, I've just got rid of this plugin and replaced it by the flat archives plugin, visible on the right hand side of this page.
Damn it! Maybe that stupid provider was right about the high CPU usage after all, but I still feel no regret having switched to Bluehost, for I know that they are more reliable and at least, they can speak proper English!