In Microsoft Access, I am receiving an error "Error Accessing File.
Network Connection May Have Been Lost." A Microsoft Knowledge Base
article (304548) deals with this problem, and it says to fix it I must
"revert to a known good backup copy of the database". A significant
amount of data has been entered since this backup, so I would prefer
to just fix the error.

A recommendation and supporting reason is needed, however the answer
does not need to provide a step by step fix, just what is generally
needed to be done.
If the answer works 100% and is relatively easy to implement, a tip
will be added.

Several newsgroup posts as well as the MSKB article you mentioned
indicate that this may not be able to be recovered from without
restoring from a backup.

Regarding the data that has been entered since the problem started,
was it imported or manually input? If it was imported then I would
suggest patching Office through the latest service pack (the MSKB
article says to patch Office 2000 through SP3), then restore your
backup, then re-import your data. If the data was manually input you
may be in a bit of a spot and need to go through the same process but
then re-input the data manually.

Newsgroup post #1:
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&threadm=3d1201c2f23c%24b0d16e30%243401280a%40phx.gbl&rnum=4&prev=/groups%3Fq%3D%2522Error%2BAccessing%2BFile%2522%26hl%3Den%26lr%3D%26ie%3DUTF-8%26scoring%3Dd%26selm%3D3d1201c2f23c%2524b0d16e30%25243401280a%2540phx.gbl%26rnum%3D4

Newsgroup post #2:
http://groups.google.com/groups?q=%22Error+Accessing+File%22&hl=en&lr=&ie=UTF-8&scoring=d&selm=037601c2ebec%2470623a10%24a501280a%40phx.gbl&rnum=11

Newsgroup post #3:
http://groups.google.com/groups?q=%22Error+Accessing+File%22&hl=en&lr=&ie=UTF-8&scoring=d&selm=Xz65NHm8CHA.2084%40cpmsftngxa08.phx.gbl&rnum=3

Newsgroup post #4:
http://groups.google.com/groups?hl=en&lr=&ie=UTF-8&threadm=OR0pkOK9CHA.3332%40TK2MSFTNGP11.phx.gbl&rnum=1&prev=/groups%3Fq%3D%2522Error%2BAccessing%2BFile%2522%26hl%3Den%26lr%3D%26ie%3DUTF-8%26scoring%3Dd%26selm%3DOR0pkOK9CHA.3332%2540TK2MSFTNGP11.phx.gbl%26rnum%3D1

Here are some additional MSKB articles that may help you as well:

Related articles:
Q304548 - ACC2000: Err: Error Accessing File. Network Connection
May...
http://support.microsoft.com/support/kb/articles/q304/5/48.asp

Q306204 - ACC2000: How to Troubleshoot Corruption in an Access
Database
http://support.microsoft.com/support/kb/articles/q306/2/04.asp

Q247771 - ACC2000: How to Recover Data from a Damaged (Corrupted)
Table
http://support.microsoft.com/support/kb/articles/q247/7/71.asp

I hope this helps, I'm curious as to what the end result is.