[SOLVED] PageRequestManagerParserErrorException on Live Server – Help!

Issue

I’m really hoping that someone can help. I have tomorrow to get this right or we’re in trouble. I apologise as I only have the details from memory, being at home.

The error is this:

Sys.WebForms.PageRequestManagerParserErrorException: The message received from the server could not be parsed. Common causes for this error are when the response is modified by calls to Response.Write(), response filters, HttpModules, or server trace is enabled.
Details: Error parsing near '
<!DOCTYPE html P'.

It appears in both FF and IE so far, and only happens on the live servers.

It occurs within partial (or attempted partial as they stop working and don’t update) postbacks within an update panel on a form that is on every page. It doesn’t always do it, but once it’s broken, it’s consistent. I have a suspicion that it kicks in after the pages in question have been posted back to by another page, but I’m not 100% about this. This form is absolutely integral to the function of the site.

I’ve googled and googled, and I’ve seen the lists of the usual causes (Reponse.Write, tracing etc.) as well as the not so usual causes (e.g. firewalls messing with headers), but none seem to apply, plus some doubly do not apply because this issue does not occur at all on our staging server. I don’t know if slower load times would affect it.

Any help would be greatly appreciated!

Edit: I’m using .net 2.0 and the ajax framework 1.0.

Solution

Thanks to Greg for his comment, but in the end I found the issue – which is indeed one of the culprits in several posts regarding this that I had looked at previously, but I missed! It was my Output Caching causing the problem, and though we’ve since looked at more aspects of the caching, this particular issue was fixed by a) turning off the caching (obviously!) or b) setting VaryByParam="*". Further info here: <Removed by OP, dead link>

Answered By – MissCellaneous

Answer Checked By – Terry (BugsFixing Volunteer)

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