Anyone notice any 'corruption' of HTML blocks over time?

[socceronly]

I sell tickets to soccer games via Pay Pal.   I usually do this by posting a block using the WYSIWYG block and then a block beneath it using HTML only for the Pay Pal button.

This is the third game where by I put these blocks up, test them and they work, then some time later the Pay Pal button stops working.  I usually just redo it.  

I can't really leave it up broken  for people to look at, because we are linked to by the national association and it isn't that big a deal to fix.

But it might be a symptom of something causing people mysterious problems....

I'll try setting up a test block in another part of the site and see if i can replicate it before entering a ticket or give something people to look at it first at least.  In this case it was almost a week before there were any problems so replicating it might take some time.  I also can't think of any changes I made to the site that might correspond to it. 

Just throwing it out there in case anyone else has any mysterious HTML block problems.